Please help! Koi problems

[tyedied]

Hi. I'm new here, but I registered because I need some help. I have a 55 gallon tank with 5 koi about 6" long and a bottom feeder a bit longer. I have I have a top fin hanging filter, keep the water at about 76 degrees, and have 2 bubble wands running in it. I have no idea as to the pH-I've never tested it because I've never had any problems except a few bouts of ick. The tank has been set up for 5 years.

Anyways, last night I noticed that my black and white koi had turned yellow-his whole head, and all the way around the edges of his body. This pretty much happened overnight. I keep a close eye on these guys. Then I noticed that another koi is starting to do the same thing. It's much paler on that one tho. The scales and texture look normal.

I've been looking on the net for answers, and I'm finding none. "Color changes are normal" doesn't work for me when the fish is 4 years old! Someone please help!!!

 

[jsoong]

Welcome to AA!!

I am not a koi person. however, I might suspect that your koi are outgrowing the tank. I think checking the water parameters for ammonia, nitrites, nitrates are in order.

I know goldfish & koi do change color as they age, but not overnight. I wonder if the fish is stressed somehow. Maybe a water change may help. Clean water never hurts.

 

[tyedied]

checked the levels. Nitrites and ammonia a little high-everything else normal. Did a half change. Keeping fingers crossed

 

[jsoong]

Nitrites & Ammonia should be always zero in a mature tank. If you detect any, it is stressing the fish. pwc is a good thing for starts, as is a good gravel vac & cleaning of MULM.

If you can't get the levels down to zero consistently, it means the bioload is exceeding the carrying capacity of your tank. Generally koi needs lots of room & really belong in a pond. Serious koi keepers will not have 5 koi in anything less than a few hundred gals. For now, lots of water changes & better filtration may postpond the inevitible, but they will need bigger digs eventually. <Kois get to be 36" or more at maturity ... so a 55 gal is seriously undersized!... Ok for babies, but you get into trouble as they grow.>