Expert: Lynda - 7/12/2009

Question
QUESTION: I recently added two angelfish to my 30 gallon aquarium.  they are in with 2 keyhole cichlids, 2 guppies, and a red-tailed shark.  I came home from work to find that my tank heater either malfunctioned or got turned up to high and the temp of hte water was 82-84 degrees.  the fish were fine except for one angel which was floating in the slight current at the top looking.  It would sim a bit and then lay over on its side a tumble around in the current untill he reached the bottom.  the it would swim quickly back to the surface with an odd wobbling motion.  It now appears to be dead in the bottom of the tank.  I am concerned that whatevercaused this could affect my other fish.  I took steps to cool of the tank by removing the heater and adding some cold water (with aquasafe) since the tank needed water anyway to replace what i lost to evaporation from my light.  Any ideas what could have caused the fishes problems and what I can do to prevent it would be greatly appreciated.

ANSWER: Hi Jerry,
The temperature would not have killed your angel.  I keep my angels in 82 degree water all the time.  You should have let the water cool down by itself, and not added cold water to your tank.  The water reached 82-84 degrees slowly, and the best thing to do, was to let it go down slowly, as a drastic change in water temperature can cause death to all fish.  The Angel that died might have been weaker than the other fish.  She should not have died because the temperature went up to 82 or 84 degrees.  There is another reason, and the reason is a mystery to me, as I did not see the fish, and apart from losing her balance, had nothing on her body.  She may have been sick, had a viral infection which would have turned up sooner or later.  
Adding an air stone would help, and check your water for ammonia, nitrites, and nitrates.  Your ammonia level should be zero, nitrites, zero, and nitrates should be low.  This is very important.
I want to mention that a red tail shark should be in a tank all by himself.  As they get bigger they are aggressive, and can terrorize a tank causing stress, and sickness to fish.  They are very pretty, but should be in a tank alone.
I hope this helps, and that they will all pull through.
Lynda

---------- FOLLOW-UP ----------

QUESTION: Good news!  So far the angel fish is not dead, I was wrong.  Right after I sent the last question in she started weakly swimming around.   The water that I added was at room temp, around 68-73 degrees. When we last checked the water quality ( about 3-4 days ago) We had no ammonia, no nitrates and A low level of nitrites ( don't remember the exact level)  the ph was a little high, around 7.7-7.9 or so.  I thought this was because I had just done a slight water change and added new water to the tank ( about 2-3 gallons)  So far I have been relying on my local fish store to test my water for me.  I do plan on buying a test kit soon though.  I can't see anything visually wrong with the angel and I checked her gills and they were a little red but not much.  Hopefully she will make it through the night.  I appreciate your help and all the previous advice you have given me in the last couple of weeks.

Answer
Hi!
I'm very happy to know that they all made it.  The angel might have lacked oxygen for a second or two.  
Your PH is very high for the fish that you are keeping.  It should be around 6.5 to 7.0.  Adding driftwood to your tank would bring it down a little.  If you do add driftwood, soak it in aquarium salt in a bucket to clean it for a week or so.  Never use chemicals to bring down the PH, such as PH down, as it never helps, and makes things worse.  You don't want your PH to fluctuate.  Maybe there is something in your tank that is causing such a high PH.  Do you have sea shells or coral in your water?  If you do this would cause the PH to go up.  It would be best to remove them.
I hope your little Angel makes it.
Lynda