Sick angel fish

[dolphineducator]

Hi all. in the last week I had two of my large angel fish die. They seemed to be healthy and then they started to float with the mouth up and their tail down near the surface. they didn't really move much and then the next day I found them dead. They didn't have any spots on them or look of a parasite. I have a 20 gal long with some loaches, 2 catfish, 1 algae eater, and another small white angel fish.
Now my small white angel fish is doing the same thing. All the other fish are fine. any ideas what is wrong?
I have a undergravel filter and my tank has been set up for about 6 months. I do a water and gravel vacume at least once a month sometimes more.
I live in Hawaii so I don't have a heater in my tank but it has been colder and I wonder if this could have affected my fish. Any ideas? Thanks.

 

[Zagz]

Do you have a test kit? You need to test your water for ammonia, nitrite,nitrates & ph. Water changes should be done once per week of at least 25%, most of us do more than that at a time. What is your current temp? Did it dip more than a couple of degrees in a short time? Any gasping or behavioural changes other than what you mentioned?

 

[dolphineducator]

I do have test kits and all are in the normal ranges. I'm not sure about the temp as I do not have a thermometor. No werid breathing. The small angel did not make it. I just want to know what it may have been so I can fix it. I love angelfish and dont' want them to die. Thanks for any help. Lia

 

[Jchillin]

I'm not sure about the temp as I do not have a thermometor.

How are you regulating the temp without one? A thermometer is an essential piece of equipment, please get one. You could be having temp swings without knowing it.

In the meantime, it will be difficult to diagnose what the actual cause of the Angels death was. At the beginning of this forum, there is a selection of critical questions which need to be addressed in order to help you out. Give them a read and post the answers here.