Tank With Yellowish Water And Brown Sludge On The Filter

[Z3RO]

I have been having this problem for several weeks. I get a cloudy tank (milky white) which im assuming that the tank is cycling. Once the cloudyness settles the filter gets covered in brown sludge and my water turns a ugly yellow.. I have been making frequent 50- 60% water changes and cleaning the gravel but I have the same problems come up every few weeks.

20 gal tank with 6 4" koi

 

[jglover]

I have been having this problem for several weeks. I get a cloudy tank (milky white) which im assuming that the tank is cycling. Once the cloudyness settles the filter gets covered in brown sludge and my water turns a ugly yellow.. I have been making frequent 50- 60% water changes and cleaning the gravel but I have the same problems come up every few weeks.

20 gal tank with 6 4" koi

I'm not positive about what is causing the water issues, but I will guess it has to do with your stocking. Having 6 four inch koi in a 20G tank is *way* overstocked. Koi and all goldfish are messy fish which generate huge amounts of waste. The typical recommendation for a single goldfish/koi is 20-30G minimum, with another 10 G for each additional fish. So realistically you should be looking at somewhere around a 75-90G gallon tank as a minimum for these fish.

How long has the tank been set up? What are your water stats (NH3, NO2, NO3, etc.)? Also how much filtration do you have on the tank? It sounds as if the filter is unable to keep up with the amount of waste generated by these fish and you are getting some sort of repeated mini-cycles in the tank.

John

 

[Corleone]

Bigger than that for koi - 10 gallons+10 per fish is for fancy goldfish. Common/comet/shubunkin goldfish need more, and koi need vastly more. A full grown koi from what I've read is between 100 and 300 gallons of pond stock depending on who you ask, and at their adult size, they'd take an aquarium almost as wide as my 55 gallon is long to turn around in.

Return the fish - they're very long lived (it's not unreasonable to expect a healthy koi to outlive its owner), but unless you've got a pond ready for them in a few months, you don't have nearly enough space for one, let alone six koi. Do a fishless cycle and either get small tropicals or one, MAYBE two fancy goldfish.

The cloudiness in the water is a bacterial bloom, which as jglover says is usually from ammonia in the water. Yellow is from fish waste, as well. The bloom itself is harmless, but the conditions that cause it usually aren't. The brown sludge in your filter is the bacteria that process ammonia. Over time it can get quite thick - I only recently noticed that the filter media in my mature tank is much heavier than the media in a new filter.

 

[Efren]

I have been having this problem for several weeks. I get a cloudy tank (milky white) which im assuming that the tank is cycling. Once the cloudyness settles the filter gets covered in brown sludge and my water turns a ugly yellow.. I have been making frequent 50- 60% water changes and cleaning the gravel but I have the same problems come up every few weeks.

20 gal tank with 6 4" koi

what else is in the tank--
IME mopani wood/bog wood
make water brownish
but it's not harmful though--
and it makes the filter sponge-- brownish/yellowish too...