FW Parasites? (RMF, second opinion on the photos) 10/20/2009
Hi Crew:
<Hello Carla,>
During the past couple of months, one of my tanks has been experiencing numerous fish deaths resulting from what appear to be bacterial infections. The first to succumb was a White Cloud (Tanichthys albonubes). The next five were all Threadfin Rainbows (Iriatherina werneri). The symptoms would begin with a small whitish spot on the body ringed with red, then over the course of 7 - 10 days, the spot would spread, and I would begin to see bright red streaks around the eyes, gills, and/or base of fins (which I believe is a sign of septicaemia).
<Can certainly be the case. Can also occur as a reaction to environmental stress, the equivalent of sunburn or chemical burns on humans. All the redness means is that superficial blood vessels have become expanded or congested.>
I also occasionally saw stringy white feces on some of the fish.
<Again, this can mean a variety of things, from constipation through to Hexamita infections.>
At this point I would euthanize the fish with clove oil, but on a couple of occasions the fish died on their own. The deaths occurred one after another, not concurrently, with usually a couple of weeks between deaths.
<I see.>
At the first sign of infection, I would transfer the ill fish to my 10-gallon hospital tank, and, since I don't have much faith in antibiotic baths, treat with either Metronidazole mixed with food, or Jungle Anti-bacterial Medicated Fish Food (Sodium sulfathiazole 2.3%, Nitrofurazone 0.13%). (The fish were still eating well during the first week or so after infection.) This treatment had no effect.
<It's worth mentioning that while antibiotics can help with some (mostly opportunistic) infections, there are some primary infections, such as Mycobacteria, that are essentially untreatable.>
I realize that most bacterial infections are a sign of poor water quality, and this has me puzzled, because I am fussy about my fish. The Threadfins were even spawning within days of getting sick.
<Interesting.>
Parameters are as follows:
-40 gallon tank
-Ammonia: 0
-Nitrite: 0
-Nitrate: 0 (heavily planted)
-pH: 8.0 - 8.2
-Temperature: 25 C
-Hardness (my KH/dH test kit is in the mail, but according to our City's water quality report, the water is very hard).
-Remaining tank mates: 3 Black Mollies, 5 Dermogenys pusilla, 5 Cherry Shrimp, 1 Threadfin Rainbow (the last one), 1 White Cloud (also the last one), 1 Scarlet Badis.
-15% weekly water changes (I don't do the usual 25% because of the Halfbeaks' sensitivity to water chemistry changes).
<Fair enough.>
Since I feel my water quality is good (although perhaps the pH is too high for Threadfins and White Clouds?),
<Yes, your pH/hardness is a bit high, but in itself, this shouldn't be killing them.>
I thought perhaps a parasite was responsible for making the fish vulnerable to bacterial infections. I do on occasion see the fish flash, although oddly, never the Threadfin Rainbows. There was never any sign of Ich or Velvet. So I pulled out my old microscope, and took skin scrapings and gill samples of three of the deceased Threadfin Rainbows. Since I really had no clue what I was doing, the results of the first two fish I examined were "inconclusive." However, by the third fish, I felt I had enough practice to get an acceptable wet-mount and take a few rudimentary photographs. I would really appreciate it if someone could take a look at the attached photos and determine if there is anything suspicious. I have placed arrows near things that look suspicious (to me), but I have no experience with this and they could well be normal microscopic detritus.
<Indeed. I am not a microbiologist. I've asked Bob to chime in here. While "scinscraping1.jpg" and "scinscraping2.jpg" have circular cells in them reminiscent of the Whitespot parasite Ichthyophthirius multifiliis, I'm not enough of an expert to confirm that either way. I will make the point here that both Whitespot and Velvet are dangerous precisely because they break the skin and make the fish vulnerable to secondary infections.><<Does appear to be Ichthyophthirius... RMF>>
Please note that my microscope is a very inexpensive unit, and probably not very good, and I took the photos with my digital camera stuck up against the eyepiece, so the quality of the micrographs is not great.
<They look great to me!><<To me as well. RMF>>
If you have any tips to pass along to improve my microscopy skills, that would be great!
Thank you so much, and thanks to all the crew members who take the time to help aquarists and their charges!
Carla
<I can't offer any easy diagnosis here. I'd do a couple of things myself though. Firstly, I'd not buy either of these fish from that particular retailer again. Or at the least, not from the current batches. Obviously both White Clouds and Rainbowfish need to be kept in schools, but I'd sooner leave them as singletons for now than risk mixing them with any more possibly infected fish. I'm saying this because it's possible that whatever is killing your fish came in with these newcomers. If you can get some of these fish from a new batch a few months from now, or immediately from another retailer, then that might be an option. Either way, I'd buy one species at a time, and quarantine them for, let's say, a month in the 10 gallon tank. I'd maintain that tank as per treating Whitespot, i.e., heat (28 C/82 F for the White Clouds, and 30 C/86 F for the Rainbows) plus a little salt, 2 to 3 level teaspoons of salt per gallon. This won't stress the fish at all, but will help deal with any Ick or Velvet parasites. After a month, it should be clear whether the fish are healthy or not, in which case, you can move them to the display tank. Hope this helps, Neale.>