Looks like my fish are dying, please help

Question
Hi, I have a tropical tank with a small finrot issue.  Today I changed 25% of the water and added the relevant treatment for finrot and water treatment, but since doing the change/treatment alot of the fish are swimming upside down, lying upside down on the bottom, lying against where the water filter goes is and in particular my clown loaches and some larger fish are just lying on the bottom looking as though they are dying (the clown loaches do this regularly I know, but normally move if you go near the tank - on this occasion they look like they are gasping and cannot move).  Also one of the clown loaches appears to be gasping at the top and banging into the tank swimming upside down.  Have you got any ideas what has happened?  I'm desparate as I don't want all my fish to die.

Answer
Good evening Lesley, thank you for your question.

Fin rot usually presents itself as a symptom of water quality troubles, namely ammonia/nitrite presence in the water. In a cycled, healthy tank, these levels are always 0 ppm. Nitrates are best kept under 20 ppm, but the former two *need* to be at  0 ppm, otherwise the medication will not only not be efficacious, it will react adversely with these substances. The 25% water change was a smart move, but more than likely more water than that needed to be changed.

The money on the medication would have been better spent on a liquid water test kit, such as the kind API makes. Fin rot normally heals itself, perhaps with the addition of salts and extra aeration. Medication is a last resort, and medicating in the main tank is not recommended, since fin rot is not contagious and antibiotics kill off the nitrifying bacteria that keeps your tank cycled.

What you must do as soon as possible, is remove the medication from the water and perform a massive water change. Change your filter cartridge or add activated carbon in a mesh bag or pantyhose, to your filter unit. Then perform a 50% water change. Test your water as soon as you can, I'd be willing to bet there is ammonia presence right now - highly toxic! You must take care of the immediate water quality issues which are suffocating your fish (ammonia presence is toxic to fish because it prevents absorption of oxygen in the blood) and then evaluate your maintenance routine to prevent future troubles.

Weekly, change 20% or more water, depending on your stocking level, with dechlorinated tap water. Use a dechlorinator such as Prime - do *not* use a dechlorinator that also removes ammonia, this is problematic in the long run.

Weekly, rinse the filter cartridge or media. Every two weeks replace it, if it's a disposable kind. Also every two weeks, vacuum the gravel. Some folks only vacuum half at a time. Strive for twice, but at least vacuum the gravel monthly.

Even if you are on top of maintenance, an overstocked tank will have constant water quality issues. You mention you have large fish. How large? I can't comment on your stocking scheme right now, since you didn't mention how many gallons or what kind of fish you have in your aquarium. If you'd like me to comment, just write back with this information.

For now, take care of the immediate problem by effecting the necessary water changes, removing the medication using carbon, increasing aeration (via an extra airstone) and add some aquarium/kosher salt to the tank at 1 teaspoon per 10 gallons. This helps with stress and nitrite toxicity.

I hope that helps! Have a nice weekend.
Nicole

P.S. If you haven't already, check out this site: http://freshaquarium.about.com

It has fishkeeping information for all levels of expertise. In this hobby, those who read are more likely to succeed!