barbiedee

I have a 55 galon freshwater tank. It's been cycled for some time now. Added 24 neon tetras, 2 pearl gouramis, 4 dwarf gouramis and 7 baby angelfish (1-2") over several months. All the fish seem to get along well...no fin nipping noticed. The dwarf gouramis and angelfish are doing well...angels are the newest and still getting used to the tank. But every morning I would find one of my neons dead or dying with rapid open mouthed gasping. My 2nd pearl gourami died this morning in my isolation tank...he had pale sections on the dorsal region of his back. What's going on??? Can someone help?
pH = 8
Temp = 75F
NH3 = 0
NO2 = 0
GH = 100mg/L
I'm doing regular water changes....ammonia and nitrite levels are never up.
Water is crystal clear.
If someone is willing to help me out I would greatly appreciate it....I hate losing all these beautiful fish.

caddyman

It's hard to determine exactly what could be causing your fish to suffer after the water change. But it could be several things-
~Improper dechlorination~
Sometimes water supply companies put far more chlorine/chloramines than normal, especially in hot summer months when bacteria in water can be at it's highest. It's always good to overdose water conditioner everytime you do a water change--especially as the weather heats up.

~Hot water gas~
I would imagine you mixed hot and cold water together to come to a proper temperature with your replacement water. Hot water hols less dissolved gas than cold water, so when water from the household plumbing passes through a water heater, it wants to release some of it's dissolved gasses. A pressurized system holds more dissolved gas than an unpressurized system. Because household plumbing is pressurized, the hot water can't release excess dissolved gas and thus holds more gasses than it normally would. So when you turn on the facet, the pressure is released and the extra gasses condense out of the solution. These gasses form bubbles all over the aquarium and even on the fish themselves. This is a danger because oftentimes the bubbles also get into the fishes gills and into the bloodstream that way. And the result is the same as when divers get "the bends" when nitrogen bubbles condense out of solution in the blood vessels. This shouldn't ever happen if the water was previously splashed a lot before adding it to the aquarium, as this will release nearly all the gas. But say you used a refill hose and had the end underwater, the bubbles couldn't dissapate. This is just a guess and I cannot say it's a sole factor.

~There could have been heavy metals in your water as well that perhaps your water conditioner didn't remove.

There are many reasons why fish gasp. As you know insufficient oxygen. But also ammonia will cause fish to gasp at the surface and such. Fish affected by ammnonia will also be very lethargic and may lay at the bottom of the tank. Are you certain your test kits aren't giving a false reading? It is possible that after this water change, you could have stirred up much debri or even released "toxic spots" in your gravel. There can be spots in the gravel that can be very well clogged with debri and become anerobic or "without oxygen" this is where anerobic bacteria florish and by metabolic processes, release toxic hydrogen sulfide that can just about poison the poor fish. But if you thoroughly vacumm with everywater change this may not be the problem.

It is possible your tap water contained some sort of toxin that you cannot test for and wont be able to. :(

~Have you tested your tap water for all three parameters?
Could the pH or hardness have been vastly different from your aquariums?

~It is also possible that something from your hands or arms could have contaminated the aquarium if you didn't rinse them very well before cleaning your tank. Any lotions, soaps, chemicals of any sort can get into your aquarium from a trace amount on your hands. If you think this may be the problem I would do another water change as soon as possible! at least 50%.

So what to do NOW?
All you can do is try your best. If you can add a ammonia neutralizer just in case that's excellent. Stress coat does not remove ammonia which can be released in fact when the chloramine bond. Or if you have zeolite add some of that to your filter too. The best you can do is add a very good amount of water conditioner/ammonia neutralizer. Add an airstone if you can or make sure at the very least that your power filter is providing very good water movement.

barbiedee

Hi...thanks for getting back to me so quickly.
I run hot and cold water together into a pail...so should not be a problem...lots of bubbles created. ph and hardness, ammonia and nitrites are steady at 0.
Tap water tests the same as tank water.
I don't clean the inside of the tank manually...have algae eaters and a magnetic block to clean the front.
I have 2 blue dwarf gouramis and 2 dwarf flame gouramis and I'm wondering if they are bullying the fish at night.
I had to remove an angelfish tonight...it's tail fin had been damaged.
Thanks again for the help.