Don't feel too bad. You couldn't have known that would happen. My betta had no problems sharing food with my neons when I kept them together in a 10-gallon tank. I think it'd be fine if you put two pyramids on either end of the tank next time.

Normally I would give him time to see if he recovers, but if he's already that bad, I would euthanize him. There are different methods for this, and you should read around to decide which one is best for you. There seems to be a bit of controversy over the different methods. I've had success putting water in the freezer until it just begins to form ice, then dropping the fish in. It takes it only a second to die, and while I imagine the sensation is horrible, it's still better than wasting away.

I'm not sure what kind of tetra that is, but be sure to replace it in the school since most of them will become aggressive if not kept in large enough numbers.

Are you sure it was an attack and not fin rot? Those block type feeders have a bad reputation for killing the bio-filter. Minimally they can create a bad algae problem or whack out pH. I would check water parameters to be sure. Are the day-glow tetras the kind that have color injection or are they glo-lights, or head and tail light (I always get them mixed up)? Anyway, the color injected ones don't last long to begin with because of the artificial coloring process. More recently I bought a battery operated auto feeder from wally world for about $10. It works great. I only have flake food in it but my fish will eat anything. If you use one of these I reccomend getting 2 weeks before your vacation so you can make sure it works properly and you have the correct setting. I have left my fish over a week before with no feedings and never had any attacks. Not all circumstances are the same but, more often then not those feeders end up being the cause.

Whoops. It is a glo-lite tetra... The reason I didn't think it was fin rot is because none of the other fish were unhealthy in the least. And all the water parameters were safe... And I actually witnessed the Betta go after him and take a chunk out of him when I was observing the tank upon returning from my trip... I'm afraid he may have picked up some kind of stress desease from this whole ordeal, but I am nervous to treat w/o knowing for sure... Right now he is laying on his back in the QT tank... He can't move w/o fins... I put food next to his mouth and he tries to eat, but it is hard for him, and I'm not sure if he's eaten anything... I'm trying to minimize stress at this point... should I medicate him, maybe half-dose? For what? Should I wait it out? Is there anyway I can feed him without him having to chew?? Maybe something that he can absorb through his skin?? I am desperate... and sad...

Jenny

Oh, noooo!! I just went and turned the tank light on, so that I could examine the fish more closely, and now he has a secondary fungal infection on his tail injury... How does one treat a fungal infection... ? I don't even know if I'll have the right meds for this... I'll go check right now...

Jenny

Well, I had some aquari-sol, so I used the full dosage, and I returned to check-up on the little guy an hour or so later, but he didn't make it... I was reading up on fungal infections on the web, and apparently, the prognosis is NOT good for body fungus, so I am actually kind of relieved that it was quick. I probably just should have euthanized as Kitty suggested... thank you all...

Jenny

I have also known of those feeders to completly change the water peraniters especially in smaller tanks. I would recommend doing several 30% water changes about three days appart. At the same time add a good Bio Starter/Cycle at the recommended dosage this will bring the good bacteria back to what it should be.

Finally in the future give them a good feeding before you leave and a few days with out food would not be a problem to them at all.
A good medication to have on hand at all times is Pimafix and Melafix.
Keith