Chillin' on the cheap...er
Hi
I followed all your directions to the tee and we have a beautiful and amazing 110 gallon reef tank with great lighting, etc. It's the most amazing sight changing daily.
My new problem is that we live in Florida (native New Yorkers) and no body said anything about a chiller. After reading a number of articles I know we can't maintain a temp. below 80 through out the summer. Now after spending a small fortune on this tank, what would be the most cost effective way to keep the water temp. down to an acceptable temp????????? I see chillers go for $600 and up?????Of course once again I need your help.
Thanks Connie
>>
Hmm, well, if the house itself is air-conditioned, or stays sort of cool... I would schedule (like with timers, dimmers) your lighting to come on in the evening... and leave it off during the day...
And, of course, there are a few degrees to be saved/lost by evaporative cooling... leaving the top off... splashing water in a sump... blowing a fan across the water's surface (anywhere)...
For "disastrously warm" days (where the water is getting over 85F.) floating a previously frozen milk jug of ice can save a system... for emergencies only...
And otherwise, just allowing the system to get warmer (low to mid eighties F.) is generally not a big problem (a little more maintenance) for true tropical set-ups (same old reference to coldwater organisms that are sometimes sold as warm in the trade... avoid these...)
Bob Fenner

DIY Chiller Questions
Bob,
I have a question for you. I am setting up a tank (not a reef yet!) but my room is extremely hot (water temp is about 83) and eventually I would like to have it as a reef tank. I don't have any experiences with chillers and
am finding difficulty with getting info on them.
<Hmm, actually, I might just go with the temp. of low eighties, and stock tropical organisms that can/do have this thermal range.>
A few questions
1) Can I place the chiller under my stand? I think I have the room.
<Yes, as long as you also have adequate air circulation too.>
2) How much noise do chillers produce?
<Good question... some are really noisy... others almost undetectable... do check specifications for this AND the first-hand reports of other aquarists who have used the units.>
3) Does the chiller itself produce heat thereby heating up the room and the
tank (in effect working against itself!)
<Oh yes... same old second law of thermodynamics at work here... And as stated above, you do need to contend with the waste heat generated...>
I can send a picture if it would be easier.
<Maybe not necessary... do consider a few loops of flexible tubing from a pump, canister filter to circulate through a small refrigerator... or just floating a frozen milk jug of water or such container on the hotter days...>
Thanks in advance....
Derek
>>
<Bob Fenner, who has been diving in places with warmer water, and wishes he was there right now.>
Thanks Bob...
The 83 degrees is without Metal Halides...so I am expecting it to jump up to
87 if I install those....
<Look into compact fluorescents instead... much cooler, and will work.>
Hmmm, I may have to consider running tubing outside the house or trying the IY chiller.
<Maybe... I even used an old flat immersed coke bottle cooler once...>
Looks like a fun challenge.
Derek >>
<Be chatting, Bob Fenner>
The biggest challenge of course is to not have tubing running where my wife can see it!!!!
>>
Understood... a bit of something here... I obfuscate such "new" occasions with the presentation of something for (wife) Diana or the household itself...
Bob Fenner, surreptitiously
Good Idea.....
I got my temperature down a few degrees by leaving the doors open on my stand. I think I will go by a couple exhaust fans today while I look for a small fridge.
Derek >>
<Ah good to hear. Simple flexible polyethylene should do for transfer properties.
Bob Fenner>

Tiny, tinier, tiniest fridges
Bob,
Sorry to keep bothering you but what is (or where) is the smallest fridge
you have found?
Derek >>
Hmm, Home Depot or like, or Costco, Sam's type outlets. 
Bob Fenner
Found something I think will work...it is made by igloo and says it will
cool the inside compartment 40 degrees below ambient temperature. I have a
225 gallon tank so I am not sure if it will cool it enough....but there is
hope. Will let you know how it goes.
>>
Hmm, this is probably way too puny a unit... be cautious here... the air and solids you might place in such a "cooler" have far less thermal mass than hundreds of gallons of water... I do suspect that passing the system water through such a device will/would have negligible effect/pull down on temperature of your system water. And, also importantly, look for efficiency in these devices... can be very expensive to run in the long haul... either a small fridge that you can build an immersion coil into or a chiller for the express purpose is what I recommend.
Bob Fenner, who says, use your search engine... at least read through the Aquanetics pages on such issues.

Geothermal Aquarium Chiller
Hi Bob!
Since we had a few days of REALLY hot weather here in the northeastern US, I am thinking of incorporating a chiller into my system.
I have a 300 gallon reef tank that is doing well (thanks to your advice and lots of hard work!). Recently, the temperature swings in my system have been getting a little high: 78 degrees in the AM to 83 degrees in the PM.
I currently use an air conditioner in the adjacent room behind my tank with fans to blow cool air into the canopy but this is both noisy, cost inefficient, and above all not able to sustain constant temperature in my tank.
My lighting consists of 4 X 250 W and 2X 400W Metal Halides. I could use shorter photoperiods and move the lamps further away from the water surface, and set a higher average temperature in my Octopus 3000 (say 81 degrees) to minimize the temperature swings but I think that I would still need those noisy fans and the inefficient air conditioner.
<Yes, likely... and setting the low temp. to 81 would likely boost the higher temp. a degree or two...>
I have an idea that could solve all of my problems with heat dissipation. I am researching a way to build a geothermal aquarium chiller (maybe I will
put those chiller manufacturers out of business !!!!). 
<And the utility companies!>
According to my research, the earth's temperature in my region of the country, is constant at around 55 degrees at a depth of around 3 to 6 feet.
If I bury a long pipe at this depth, say 100 feet in total length, and then connect it to a pump and to my aquarium, voila....free cooling except for the electricity to run the pump (and the elbow grease to dig the trench
;-( ).
<Neat idea... will you use polyethylene, ABS... tubing? Any transfer medium... like water around the area...>
I think I would need a valve that is thermostatically controlled so that I could restrict cool water flow into the aquarium when the temp gets too low and to allow maximum water flow into the aquarium when the temp is too high. Depending on the temperature differential of the tank water and the cooled water, this valve may or not be needed. The important thing is to:
<Mmm, would try this out w/o the valve, switch for now...>
1. bury the pipe below the frost line
<Mmm, above the frost line>
2. always keep the water moving thru the pipe to prevent freezing in the winter.
<Well... would abandon same in Winter myself...>
Does this all sound do-able or does this seem like a pipe dream to you (no pun intended) ? Do you know of anyone who has tried this yet and has been successful ?
<Haven't seen this yet. Press on. Bob Fenner>
Thanks Again
Chuck Spyropulos

Water Cooling
Hello Bob,
<Jerry... Anthony Calfo here pinch-hitting for Bob>
I am hoping for an opinion on a project I am starting in the next week. I have a 180 gallon reef tank. I currently use a typical chiller. It is expensive, noisy, puts off heat, etc. I am also building a new house. I intend to bury tubing under the basement or garage floor, through which I move aquarium water to cool it in the summer. 
<what kind of tubing... plastic and vinyl are poor conductors... may be cost-prohibitive to compensate for with bigger pumps and longer tubing>
I plan to use my existing Medusa controller to control the circulating pump. I will have a low point so I can easily drain the loop during the winter or other periods of non-use. I was hoping to make it an open system with the saltwater going directly through the tubing. An alternative would be to use another container to do the heat transfer (closed system), allowing me to use non-toxic antifreeze
<interesting and still scary>
for the fluid I'm circulating, thus avoiding any risk of stagnant water or outgassing problems from the tubing or the risk of losing water from the reef if the water leaks out of the loop somehow. I was planning on using polybutylene tubing but I have read that much of the tubing allows oxygen to permeate. If the tubing is buried within a concrete slab, is oxygen an issue? 
<if so, you have a greater concern with other ground contaminants>
Does the concrete leach anything into the tubing?
<raw concrete. perhaps. Honestly not sure in general>
Any input you can give me would be highly appreciated.
THANK YOU. Jerry Moeller
<Jerry, many diligent folk have come before you trying to re-invent the wheel on this issue. Some success can be had with evaporative cooling principles... but the poly tubing approach has failed many times before. I honestly think you are taking the long way around the barn. If you use a chiller, place the unit near the ceiling if in the same room, or better yet put it in the next room above or below the tank's room to exhaust the heat. Do not encase the chiller for noise reduction as this will reduce efficiency and be cost-prohibitive. Open canopies, exhaust fans (evaporative) and larger external recirc pumps on a manifold (instead of many submerged power heads for water movement) will all help you reach your goal. Kindly, Anthony>

A new DIY chiller
Hi Robert
Just a note to let you know that I have a new DIY chiller at http://chiller.nickperkin.com
It is different to other chillers in that the fridge is on all the time but the powerhead only circulates the water when the temp gets to high.
I hope you can add it to your DIY page
<Well done. Thank you for sending this along, and making it! Will place. Cheers. Bob Fenner>
Nick Perkin
Sydney, Australia
www.nickperkin.com

Re: Quick question re: Chillers
You mention chillers, and although this isn't entirely related it brings up another question. I've been toying with the idea of keeping a cold water "local" area tank (stuff from Maine and New Hampshire...) but I don't want to spend the $600+ on another tank at the moment. I was playing around with the idea of making an alternative chiller, namely using my old college fridge and pumping the water through a bunch of coils inside the fridge and then back into the tank. Do you know of any sites I could check out to get info on this idea? 
<Don't know of any... but have done this sort of "immersion" bath, exchange tubing myself... Please read: http://www.wetwebmedia.com/marindind2.htm re Coldwater Marine Systems, the FAQs on Chillers>
I know it's not the first time this has been done as I got it from some article I saw a few years back (just can't remember where).
<Done... many times>
The other question is in regards to those chillers that you float on the surface of your sump. They are fairly inexpensive (under $100) but I have yet to find out much about how well they work. The thing is that I'm running a 65 gallon show tank with a Rubbermaid sump (40 gallons???) and a 29 gallon refugium and I actually have trouble keeping the temp up! I've been keeping the temp at roughly 80-83 but that's with two heaters running (both smaller heaters that happened to be laying around), any ways I've never had need of a chiller so I have limited knowledge of them.
Brian
<The stated temperature is a bit high... the "on top" chillers I have seen have not been worthwhile except for very small or very large systems (different makes, models). The Titanium tubing/exchanger models are the best currently for functionality, return on investment. Bob Fenner>

Home made chillers
Greetings, I have an idea I want to run past you guys. I currently have a 125 gal. tank that gets up to the low 80's and I'd like to bring it down to about 75 degrees.
<75 is too cold. I am not a big proponent of pushing the envelope with increased temperature, but I would keep the tank at 78. Even as high as 82 if I had a chiller and good control over it getting higher than 82.>
Here's my idea, I'm planning on buying a deep freezer with a storage capacity of 5 cubic feet, about 30-40 feet of 3/4 tubing (coiled), a Rio 1400 pump to circulate the water through the freezer, plumbing accessories (elbows, etc.), & a heater for the wet/dry to stabilize the temperature. Without reaming me like last time what's your opinion on the pump, length of tubing, & any ideas on will this $200 setup work? My return pump is a Rio 4100, I have two 72 inch VHO lights, & I plan on doing all of the connections from the wet/dry. I've read over the internet about this sometimes working with a dorm fridge, I found a deep freezer for a comparable price & it's a little more energy efficient.
<There is a world of difference between a dorm fridge and a deep freezer. Deep freezers are designed to run efficiently while filled with something to keep frozen. An empty deep freezer will use a lot of energy. Also, you have $200. I would buy a real chiller before wasting that much money on unproven technology. -Steven Pro>

UV Sterilizer and Advice (chiller, ich)
Hi Bob,
<Steven Pro this morning.>
Need your help. I have a big aquarium about 1000 liters. Currently there is only fish and livestock due to hot temp in the aquarium about 30 C.
<That is 86 F for the non-metric users.>
I planning to make a chiller out of a small fridge. Do you think this will work. I got the blueprint from Don Caster from one of the website. Please advise.
<I have seen many of these plans before. It may work, but not nearly as effectively as a commercial unit.>
I have few tangs and few angels in the aquarium but somehow is got infected with ICK (white spot). After dying of few fishes, I have used Copper Safe in the aquarium, and it seem to help but now and then the ick seem to come back.
<Sounds like you have an underlying environmental issue; water quality, temperature fluctuations, etc.>
How can I be sure to kill all the ICK.
<You will never be able to kill all the Ick. It will always be present in some small number and the fish will tolerate it. It is when something occurs that makes the parasites multiply, that puts your fish in harm.>
If I am planning to start a reef aquarium, how do I remove all the copper solution from the water.
<PolyFilter will remove it from the water, but nothing will remove it from your calcium based media; liverock and sand. You will need to remove all this and replace. The biggest reason why it is best to treat in a separate bare bottom quarantine/hospital tank.>
Will a protein skimmer help?
<Help with overall water quality, not copper. IMO, all marine tanks should have one.>
I was told also to used UV sterilizer. What voltage should be safe for my aquarium. I saw one from one of the local store that say it can process about 7000 liter or 10000 liter. But the voltage is also
9V. Are those usable for my scenario?
<Generally, I do not recommend UV's for hobbyists. They are usually ineffective and your money would be better spent on a protein skimmer and a quarantine tank.>
Please help as I have ran out of ideas.
Thank you very much. Cheers, Daniel
<You are welcome. -Steven Pro>

Stainless Steel
I'm wondering if it is ok to run stainless in reef tank. well ill tell you what I'm doing. I just came across a new Culligan drinking fountains the ones that chill&heat .some one dropped it broke the holder for the water .so it leaks water at top, other wise perfect so I took it, customized it. it had a 2gal.stanliss bull that water went in and chilled. so had a brilliant idea so broke out Tig wilder turned bull into perisherpot like device. no other metals in system. George tested, put small in pump I can chill and heat no problem I'm using a CAtm 3ooo sump pump in 5 gal. bucket. with a Honeywell digital temperature control wired in cooler. less then 2 min. 37 degree water heat just as fast. now on 55 gallon barrel 10 1/2 mm 37dere water . been holding 80 degree water 48hours now .played with some more designed to fit under  tank hook up in series with pluming. what to know if stainless steal ok before I attach to system. I also have another project need some knowledge .ill ask latter..
<Mmm, you could use this chiller with an exchange coil of some sort but not exposed directly to seawater... it will rust and pollute the seawater if it comes in direct contact. Bob Fenner>

Re: Stainless Steel
so stainless is no good it will rust.
<Yes>
so have to come up with some plastic liner or some sort.
<Actually... an "immersion bath" like an aquarium or tub that you can fill with freshwater, run the heater/chiller in... and a long plastic (flexible or solid) pipe that you can use as a heat exchange coil... pumping your seawater from the system through... immersed in this bath>
also want to know if there is a special glue to use on PVC pipe or just soak in salt water to get out contaminates in pipe after contraction. always use to run water threw PVC one hour in none tank constriction.
<No special glue>
like drinking water wonder the same or not. I really like your sight leaned a lot form you. thanks bob for the info. get back on other project when little more info on construction.. thanks again for your time to write me back approach the call back.
<Glad to help. Bob Fenner>

Chiller for reef tanks 5/1/03
Anthony on reef central, at reef discussion called "My chiller setup" there's a thread with pictures and it is the best I have seen... to keep the temperature under control in a reef tank. They used a window AC unit and it keeps the heat and the noise outside of the house. It would be good if the people who read WetWebMedia could read it. Would tell many how a real chiller should work and it was home made.
<thanks kindly Ralph! Will post this on the daily FAQs. Anthony>

Chiller input
To Bob Fenner- At reef central, reef discussion My chiller setup with lots of pictures by tonytooth. It was built with a 6000 BTU window unit AC and titanium chiller coil. All the heat and noise are outside, just the chiller coil inside. Bob this is the best design of a small chiller that I have seen. And it is low cost to build .All chillers build now are in one box not good Even if you do not want to build this a good one to check out. With 30 years working with chillers this one is 5 stars.                RGibson
<Thank you for this. Please send along specific URL's if/when you can, as this greatly expedites retrieval by others. Bob Fenner>

Inexpensive, dependable chiller quest
dear bob
<Howdy>
I saw my first tidepool aquarium in 1968, and have been hooked by this picture in my mind ever since.  Also blocked by the chiller dilemma at the same time.  First, there weren't any,  now, their too damned expensive. Is this a rich guy hobby or what?
<Either rich or inventive and mid-income>
I'm looking for 58 degrees 365 days & nights per year, not a cool down on a hot afternoon.   One percent of a lot of people is a lot of people.   Some of 'em got to be smart.  So where are the DIY chillers, that won't blow up in July. I don't want to use a freezer I found decide the road.  I will have to drive 100 miles to "bring em back alive" ( Portland Or.)  Don't want to find my mini monsters dead when I get home with more.
<Mmm, there are a few designs about... some on ozreef.org>
  A challenge for you Bob.  Enter the appliance store of your choice, and ask any salesman what's the HP of this freezer, or that frig. Get ready for, "Uuughh I don't know." well then, who does know. "Uuuughh I don't know". he works there doesn't he? He sells 'em doesn't he?  How, do we judge how much work a refrigeration unit can do w/out it's HP?  For that matter, how much HP is need to drop 90g of water in a 3/8 inch acrylic aquarium from 85 degrees to 58 degrees and keep it there forever, if room temp is 84 degrees.
<Or how about asking for one or more definitions of what horsepower is?>
  Grainger sells complete condenser units 1/6 to 1/4 HP for $275 to $325. I can buy
titanium tubing in Beautiful Downtown Portland.
<Are you a good welder of this metal?>
  Beats the hell out of Mystery Chillers Inc. $600 life indefinite, noise maker.  I think we could use an up grade from DIY Coke machine conversion chillers to something that will live as long as our livestock.  If substrate is getting better, how about the devise all our Pacific Ocean creepie crawlers are totally dependent on.  Surely some of your fans are engineers.  So squeeze 'em Bob, squeeze 'em.
<I think you're going to do it with this posted e-mail>
The world is good  for you in your 5000 sq. ft. home with 6 garage doors, but for those of us out here in the trenches, life is real.
<Uh, we have a double garage door, three roommates, but Di uses all the space anyway...>
We need data, dimensions, and drawings Bob.  Really, how much HP "IS" needed  to drop 90g of water in a 3/8 inch acrylic aquarium from 85 degrees to 58 degrees and keep it their forever, if the room temperature is 84 degrees..  We need plans and parts list. You know, information.  
<I'd go with the "standard" chart reply here of a good half HP, even 3/4>
It's not you fault or mine the chiller builders/seller are money groping  profiteers? Lots of industries have gone the "way" because their prices opened the door to more economy minded potential buyers. I'm dead with out an economical chiller, and I don't want  to kill hapless critters with a piece of junk.
<I wish you ran the EPA, if not the country>
  Time to take a serious look at DIY chillers? .Very grateful  for WWM.com Thank you.
               <Thank you for writing. Bob Fenner>
Terry Southwell    

Chilling, chillers
Dear Bob,
<Howdy>
Please allow me to apologize for my far less than friendly attitude expressed in my first email to you.  One of my many faults in getting angry  when I am frustrated.  I do have the means to contain myself.  Like a computer, garbage in , garbage out.   
<No worries>
     An WWM article some where  mentioned the word 'tidepool'.  This is as close as I have been able to get to the topic on the Web, or the library.  I guess I will have to think reef, and make adjustments. The problem with the chiller thing, is it's a deal breaker.  Sort of pumping salt water round and round through the filter, I can't get started without one.  Don't have a tank yet anyway, too many questions.
<Good to have>
      My attempts to get to 'ozreef.com'  have not been successful.  Is there more to the URL?  Am I looking for apples in the turnip store?
<Sorry re. The URL is: http://www.ozreef.org/>
  1 HP = 746 watts, but  how much cold, daaahhhh.  BTU = 1b of water  changed one degree F.  Will I need to know more?   Folks selling tanks plus gear are offering 1/6 HP chillers with 75g tanks. No good?  I think salesmen are the wrong guys to ask, but don't know the right guys.  If  I
<Do see the chart on Aquanetics chart: http://www.aquanetics.com/pdf%20files/fluid_chiller_asc_adic_1-4.pdf>
could afford to pay, a refrigeration engineer, I could buy a chiller.  Fish store guys with 75 degree livestock know I will be buying very little from them. I will have to make my own live rock and sand.
<And livestock too?>
Your living accommodations  sound like what I grew up in.  People with the garage doors  live on the lake. They may own chiller companies.   If titanium can be welded to copper,  I can find someone to do it for me.  I will be farming out several things I don't know squat about.  
<You are wise here. No welding these dissimilar metals as far as I know>
I caught tidepool mini monsters as a child, and took them home in a can, they died. I shot a bird with BB gun, it died.  That's enough great white hunter for me.  To keep them alive and 'happy'  is a better goal.  Leaving them  where they are is a higher goal,  but gee whiz Mom, a guys  gotta  have somthin' to do.  
<Yes... to err as in to wander/wonder is human... many other possibilities... making pictures, writing, telling stories...>
Any thoughts about reliable methods of keeping  100gal of water at about 60 degrees forever would be greatly appreciated.   Thank you,  and thank goodness for WWM.com
<Really, the only consistent, reliable method (barring a thermal sink in areas where the ground is cold year round) is to employ a compressor type expansion, heat exchange... chiller unit, with a thermostatic mechanism. Bob Fenner>
Terry Southwell

Aluminum
Hi Guys
Does anyone know what type of aluminum pipe if any can be used to plump salt water (any type of corrosive problems).
Currently in the process of designing own chiller.
Thanks..........Wayne
<As far as I'm aware, all aluminum is toxic, corrosive in/near seawater. Chiller transfer materials are generally titanium, but can be made of vinyl, PVC... in an immersion bath arrangement. There are a few places over the years that I've seen plans, dream-designs for aquarium chillers... but the above general statements are valid. Bob Fenner>

Cold water marine aquarium
Dear Mr. Fenner,
<Mr. Farrell>
Some of the following questions are probably unfair, but you have such a great website (and good site sponsors) I can't resist asking them.
<Ask away>
Twenty five years ago we set up a 25 gallon cold water marine aquarium for Pacific NW intertidal life in our living room. It had a beach sand filter bed laid over Tygon tubing coils circulating antifreeze cooled by a surplus brine chiller, and a homemade external filter containing floss and activated charcoal.
<Quite inventive>
I don't recall that we ever heard of skimmers or water testing, but it worked great for several years. The kids collected animals on the beach to stock it, and learned a lot about the law of the jungle (i.e., eat or be eaten). Eventually, the kids went off to school, the chiller broke, the equipment was scrapped, and we were just left with a lot of salt deposits in the living room.
Now I've been given the challenge of setting up a similar system in our granddaughter's elementary school. Operation needs to simple, since I live several hours from the school. Also, it may be necessary to shut down each spring and restart each fall.
<Ah. "Things" have improved>
We have a 35 gallon glass tank, 4 feet long, and a surplus chiller. We plan to skip the undergravel filter, and just use a commercial external filter (probably Fluval or Eheim) and a skimmer. No air injection beyond that required by the skimmer. And, I assume, no wet/dry filtering to minimize heat gain?
<Not essential, no>
I've learned a lot about modern marine aquarium technology and chillers from your great web site, but still have several questions.
Is any of the Wrobel material on cold water tanks available on the Net? Our Seattle libraries, including the University, don't have anything except his text on gelatinous animals.
<Not as far as I'm aware, and that's a shame>
We are planning to use an inch of local beach sand on the bottom of the tank. Would it be beneficial to use maybe 1/3 crushed coral with the sand to help keep the calcium level up?
<Perhaps. You can monitor this level and augment in other ways if necessary>
Should I insulate at least the back and bottom to reduce heat gain? What material is best; I was thinking foil-coated building foam? Should it be sealed to the tank with caulk?
<The insulation is a good idea. Your choice is excellent. Simple rubber-cement will do fine... is easily removed if wanted to later>
I assume amateur double glazing the tank front and ends can lead to problems?
<Yes. I would not do this... professional systems, public aquariums sometimes avail themselves of such, with a desiccant in-between... but largely unnecessary in your circumstances>
But are there any successful low-cost schemes to reduce the sweating and condensate runoff?
<Best to do what is practical to reduce the ambient moisture in surrounding air... in the room about the tank>
Our new chiller has a copper to copper heat exchanger, so I will need to add a secondary exchanger using plastic or titanium tubing. I prefer titanium tubing over plastic because of its greater heat conductivity. But can I use common 3AL-2.5 titanium, with its 3 percent aluminum, or do I have to find the much more expensive CP commercially pure grade?
<The CP... if money, time is an issue, I would elect for a vinyl immersion coil in an insulated cooler with the copper line immersed there>
I assume the thin titanium oxide layer that forms on the 3AL-2.5 makes it safe for my application, but I can't find a clear reference to confirm this.
<Safe enough in general>
In one hour our new chiller can cool 55 gallons of 59 degree water 10 degrees F, and 35 gallons 15 degrees, for an output of just over 4,000 BTU, if I did the math correctly. I assume we are trying to maintain about 55 degree water. Is this enough cooling capacity to keep us about 25 degrees below room temperature? Even without insulating the tank?
<I believe so>
Minimum chiller temperature as the water flow goes to zero is about 37 degrees, so I plan to use water instead of bothering with antifreeze.
<Yes. Avoid the ethylene glycol. Unnecessary and a hazard>
(It's a medical surplus unit designed to cool human bodies, and includes a hot-gas bypass pressure regulator that limits the temperature to well above freezing.) Because I have the tubing, I am thinking of using a single-pass counterflow secondary heat exchanger with a 1 inch OD 0.070 wall titanium tube for the aquarium water, inside of a 2 inch ID insulated plastic tube for the chiller water. Plus a few baffle plates in each tube to minimize laminar flow. Does this sound adequate?
<Yes. Even smaller diameters would work fine. But if you already possess the current materials...>
Anything over 4 feet is cumbersome to mount, but what is a minimum effective length? If I shouldn't use 3AL-2.5 titanium, how much plastic tubing might be required instead?
<"The longer the better", likely fifteen or more feet. You might posit your questions to the fine folks at Aquanetics(.com)>
How much water flow might be appropriate for the secondary heat exchanger?
<A matter of experimentation. I would hook up a small head and pressure magnetic drive fluid-moving pump and a gate valve (silicone over the metal screw in the handle) and try various flow rates. Likely 2-300 gph is what you're looking for>
And would it be appropriate to get something like a Fluval 204 or 304 filter with a built in pump and plumb the exchanger in series with it, or better to use a separate pump for the exchanger?
<I strongly suggest a dedicated pump. A multi-use application will suffer from inconstant flow rate (as the filter material gets "dirty")>
Anything important I'm missing here?
<Nothing stands out>
Sincerely,
Rich Farrell
<Do make it known how your project progresses. Bob Fenner>

-McGuivering a cooling device-
Hi : (This is for the temp-control-plumbing guru on staff tonight)
<Hmmm... well, how 'bout me instead? :) >
I'd like to know if there is a commercial device, or DIY plans to make one, that cools marine tanks down to room temps. by using simple heat sink physics, i.e. how a car radiator works.
<There's a product called an Ice Probe chiller which is a bulkhead mounted heat sink with a small fan on it. Unfortunately they're really small and impractical for larger tanks.>
I keep the house at a constant 78 degrees year round, but my tank of course hovers about 3-4 degrees above that due to the heat released by my overpriced reef lights and pumps (1 Iwaki external, 1 RIO internal.) Instead of spending $$ for a chiller, and then more $$ monthly to run it, releasing the heat from the tank into the house air would do just fine for me.
<A simple cheap Mart-mart fan blowing across the waters surface in the display or sump should give you all the cooling you need. Evaporative cooling is cheap and easy, you just need to top off more frequently (also makes having very pure top-off water imperative!).>
I know enough about this topic to McGuiver one myself, but I'd prefer to be lazy and steal someone else's previous work.
<I'd be interested to see what you come up, but I'd try a small fan or two first. -Kevin>
Thanks,
SLC