Colombian Red-Finned Tetras & Dropsy

[Steve Walker]

Interesting one, this. I've got some colombian red-tail tetras (Hyphessobrycon columbianus) in a South American community tank.

 

We initially bought six fish, and within a few days they were at it like rabbits. We soon had a shoal of fry, but we started losing the original fish one at a time to dropsy. Full-on pinecone effect with water blisters. By the time the dozen or so fry had reached about an inch, we had lost all of the original fish. As the fry have grown, they too have succumbed one by one, so we are now back to 6 fish.

 

In my experience, although dropsy is caused by bacterial infection, it's almost always down to water quality. In this case, the water quality has remained fine throughout. It's slightly harder and less acid than I would like, but well within the tolerances of all species present. I'd also expect to see other fish suffering if it were a water quality issue, but I've had no problems.

 

It's a mature, well-planted 190 litre tank with a couple of small angels, corydorus, neon, cardinal and black phantom tetras, a plec and a couple of clown loach to keep the snails down. I've tried a proprietary anti-bacterial medication, but I've no faith whatsoever in them, and it didn't work. I now remove any fish immediately they show any signs of developing dropsy.

 

So, anyone else come across problems with these critters? As far as I know they are no more sensitive than any of the other species present, so I can only guess that they brought some pathogen specific to them with them.

[MrWiggly]

Bad Stock ? Interbreeding ?

[Steve Walker]

Could be. The fish shop I got them from is one of the best I've come across, and they are pretty fussy about their fish, but you never know. I suspect that most captive-bred tropicals are as inbred as an Alabama trailer park.

[Ken Davison South Wales]

Were they captive bred?

 

If they were imported wild fish soft water would have been more critical.

 

I have captive bred colombian red-tail tetras and have top up the tank with tap water without problems.

 

The only thing that surprises me is the young dying of, being bred in the water one would have thought that minor water quality issues would not have caused a problem.

 

Interbreeding is avoided by major European breeders, if their stock goes bad on them they have to start over and that is not good news.

 

Some South American breeders do use the old stock pond breeding system which could lead to problems, you see this a lot in guppies.

 

Dropsy is very hard to cure, the method I use is to remove them to a quarrantine tank and double dose for four hours remove half the water and replace with clean.

 

The trouble with of the shelf cures is that they have to take into account that the majority of people always over dose so they are very weak.

 

The way I discribe can help fish to survive but they seldom regain full health after dropsy.

[Steve Walker]

Ken,

 

I think it's unlikely that mine were wild-caught, given that they seem easy to breed and weren't that expensive. As you say, it seems unlikely that they would breed if the pH and hardness were intolerable, usually excess hardness prevents fertilization of the eggs.

 

In the past, I've occasionally had goldfish make a full recovery from dropsy, but it's been caused by osmotic stress through a big ulcer, not through kidney failure. Quarantine, salt (to reduce the osmotic stress) and TLC. With tropicals, it always seems lethal.

 

I think I'll just have to sit this one out and not buy any more. It's a shame, because they're pretty, active (read bloody greedy) fish. Remind me of roach, a bit.

[Ken Davison South Wales]

I have some Jerdoni Barbs {think the spelling is right} they look and behave just like roach. Feeding at all levels, love to shoal, but are far to active for a community tank.

 

Yes the fact that the eggs hatched proves the water quality was near to perfect. Must be an inbred problem with that strain.

 

As a retailer sourcing quality fish is always a problem, most wholesalers want to shift the fishas quickly as possible and some outfits are very low on the quality side. I try to visit my suppliers prior to purchasing on a regular basis, but you do not learn a lot in a few hours and looks can be deceiving.

[Steve Walker]

Just googled those, you're right about the roach resemblance. I'd love a large tank with a good sized shoal of tinfoil barbs, they're gorgeous fish. Ain't going to happen in this house, though; the missus *really* wants a rift valley cichlid tank, as do I, but after much debate we agreed there was absolutely nowhere to put one. It would make a lot more sense than a soft water tank with the tap water round here, though.

 

You're also right about the retailers. The place I use is a little family business run by real enthusiasts. Some of the other outlets are scandalous. One of them had white spot running rampant in the display tanks, dead and dying fish and severely emaciated clown loach on display. They were also selling small rainbow trout (in terrible condition, fin rot and saprolegnia), barbel and chub for garden ponds.