bizarre bala shark death

Question
I have a 30 gallon tank with one tiger barb and two bala sharks in it. When i got home from school one day last week one of my bala sharks was acting very strange. It was hovering at the bottom of the tank, had red streaks in it's tail. It was fine when i left that morning but when i got back (about 7 hours later) it was like this. i left for work and when i got home a few hours later, it started floating on it's side and died within minutes. The other two fish are fine and show no signs of stress. I keep the water temp at 75 degrees and give them a diet of flakes, blood worms, and occasionally brine shrimp. I know tiger barbs are known to be aggressive, but mine has never nipped or even chased my sharks. i checked the water quality and everything seems to be about normal. I'm stumped on this and i don't want to lose another fish.

Answer
Hi Kyle,

Red streaked fins are signs of water quality issues. If this is a new tank, it may still be cycling - your fish would be reacting to "new tank syndrome" Google that, if you're unsure what it means. It can take up to three months for a new tank to become stable.

If this tank is not new, then something else is happening to make the water off. Maybe you're not changing enough water? 25% weekly is recommended, changing water weekly is a fine idea not just to dilute wastes, but to add back elements that get expended. Changing water weekly is key to having a stable pH, for example. Always use dechlorinator that removes chlorine and chloramine, this is a must - NEVER use bottled water or some other kind of "pure" water! Tap water with dechlorinator added is always preferable.

Maybe there is uneaten food or debris? I can't imagine your three fish ate much so a whole cube of bloodworms would be too much, for example, and flakes especially tend to pollute the water, which is why I prefer pellets or crisps. If you're using the "cartridge" type filter, this kind of filter gets clogged rapidly, you'll see in a week that it's full of gunk! The cartridges need to be replaced at least twice monthly. (This is why I much prefer the AquaClear media, which is rinseable and reusable...the sponges and Biomax come in different sizes so you can switch to using this kind of media in your hang-on back filter without incident, and just toss out the cartridges.)

In any case, the bala shark will really grow much too large for a 30 gallon tank, so be sure you have the provisions to trade him in. Tiger barbs are schooling fish, so this tiger barb ought to have at least two more buddies. Tiger barbs are actually most prone to aggression when kept alone - having a school of them makes them much more peaceful. The bala shark will probably be nervous alone, but I would not add more bala sharks...they need at least a 55 gallon tank, which will eventually be outgrown! They are very handsome fish, though.

Do be sure that when you check water quality that it looks like this:
ammonia - 0 ppm
nitrites - 0 ppm
nitr*A*tes - 20 ppm or less

And water chemistry should be like this:
pH - should be the same as your tap, or very close to it

That's what matters, not usually how high or low your pH is, just that it's steady, and not too different from your own tap water. Low alkalinity causes "pH shock" because water that is not very alkaline at all, will have poor buffering capacity and cause the pH to fall rapidly. *Avoid* using pH up or down products, these don't work the way you think, and usually all they do is cause your fish stress...

So check into all those factors, and if in doubt, keep changing 20% of the water daily. Vacuum up any uneaten food. You're offering a nice variety, but be sure you aren't overfeeding. Fish need to be fed a lot less than you think! All the food should be gone in a minute or so.

This website suggests all kinds of food to feed fish:
http://fish.mongabay.com/food.htm

I would be adding some extra aeration to the tank, either by using an airstone, bubble wall, etc. or placing a powerhead near the surface. Extra aeration can help your fish during times of stress.

Good luck, I hope everything sorts itself out!
Nicole