Angelfish

[mattckf]

I have a 30g tank with 6 angelfish - all the size of a 25 cent coin. They were doing very well for a couple of months then 2 just died - stopped eating and died suddenly within a couple of days. Water is 6.8 pH, nitrates 0, temp 78*F. The rest looks fine and healthy and eating. I feed frozen blood worms. Any idea what the problem may be?

 

[librarygirl]

Hi! What are the parameters: ammonia, nitrite, nitrate? 6 angels in a 30 is way too much. You'd could have one max. As they grow they are letting off more toxins and are going to become stressed in so small a space. Also without nitrates your tank doesn't seem to be cycled; is this a new tank? I'm suspecting ammonia or nitrite poisoning at this point. Try a couple of 50% water changes with dechlorinator. Cut back on feeding. Frozen foods shouldn't really be a staple food, just a treat. Try a better fish food. You'll still need to rehome most of the angels though.

Here's a couple of links for you:
I just learned about cycling but I already have fish. What now?! - Aquarium Advice
Guide to Starting a Freshwater Aquarium - Aquarium Advice

 

[mattckf]

The tank is completely cycled - not a new tank at all. My angels are still small - 25 cent coin size. I intend to rehouse them to a larger tank when they grow. Just retested water - NH3 is nil. NO2 is nil. NO3 is 5ppm. pH is 6.8. All pretty ideal. So I can't figure out what caused the 2 angels to stop eating and die. The remaining 4 looks absolutely fine and eating well. Very frustrating. Could it be due to the frozen worms I fed? I got the Hikari brand so I presume it is safe.