Some fish gasping for air, neons dying

Question
Tank has been set up since December 28th, 2006. 36 x 12 x 16, 2 platies, 5 Diamond Neons, 3 Pearl Gouramis, 2 albino corys, 1 platy, 6 neon tetras, 1 black neon.  pH 6.5, Ammonia 0, nitrites 0, nitrates 20. Weekly water changes of 8 gallons., Fluval 205 filter.  On 03/01 added 15 neon tetras. Did water change on 03/01. Lost 1 Tetra. Did 2nd water change 03/09 and forgot to plug heater back in w/temp drop of 4-5 degrees for about 2 hours.  Heater normally at 80 degrees. Now losing neon tetras daily and lost 4 of 5 black neons.  Down to 6 neon tetras and 1 black. Some fish appear to be gasping for air and staying at mid or bottom of tank (not top).  HELP!


Answer
Hi Debra;

Test the water again. I would suspect that toxins are elevated from the addition of new fish OR a case of ich got started in there from the temperature drop. It might even be both at once. Adding so many fish at one time can seriously affect the biological balance causing temporary spikes in ammonia and/or nitrites. Make a few daily partial water changes to help lower it if elevated. Replace 25% of the water every day until they drop. Nitrite spikes keep the fish from absorbing oxygen properly because nitrite poisoning causes blood changes. Aquarium salt helps to counteract it. Use it according to the label instructions.

If there are no toxins, look for tiny white dots on the fish. If they have some, treat with an ick remedy and add aquarium salt. Also raise the temperature to 82 degrees. Ick hates heat and salt.

Be sure there is plenty of oxygen in there too. Either problem (ick or nitrite) will cause a need for more aeration. Use an air pump with an airstone to help with that.

I hope they feel better soon...

At Your Service;
Chris Robbins