Can I stop this constant fin-nipping?
I bought a large group of 14 tiger barbs for my Juwel 240-litre aquarium, but they have been dying one by one due to fin nipping among them. It seems there’s always one which gets picked on, with its tail or fins nipped away so much that the fish eventually dies. I now have only 11 and one of those has been nipped so badly that I don’t think it will survive much longer.
They are kept alongside eight Odessa barbs, the two males of which are also very aggressive, although they don’t seem to nip the tigers’ fins particularly—the damage seems to be done by the tigers themselves. Other fish are a rainbow shark and three striped loaches, all of which seem fine.
What do I do? Would dropping the temperature slightly help at all? It’s currently at 24°C.
PHIL TOWERS
BOB SAYS: Tiger barbs do have a deserved reputation for being fin nippers, but it is unusual for them to do so in this sort of degree when stocked in the numbers you have. I'm also surprised to hear of aggression from Odessa barbs, Pethia padamya, which are generally peaceful fish—for barbs, anyway.
One way of calming groups of otherwise feisty fish is to add something of similar temperament, but bigger, to act as an aquatic 'bouncer', but you've already done that with the rainbow shark,
Epalzeorhynchos frenatum. I'm assuming the 'striped loaches' are a species of Botia-type loach, which again can be nippy and would fulfil the same sort of role as the shark.
This really doesn't leave many solutions that have a great success rate. The best one is still adding yet more tigers, but given the damage being done already, it's a risk, especially given that your tank is probably near capacity in terms of stocking. Ten is the absolute minimum I'd ever recommend together, but bigger shoals typically disperse the aggressive behaviour. It might mean that you either re-home the remaining tigers, or if they are your preferred species, then re-home the Odessas to allow the stocking of 20+ tigers, hoping this will solve the issue.
Reducing the temperature by a couple of degrees may slow things down a bit, and Odessas in particular are more temperate than tropical, so it could be worth a try.