For almost 6 months I've had the same problem with 3 goldfish in a 10 gallon
tank. The water would turn green within a few days of cleaning it.
Recently on the advice of someone who maintains tanks in an office, I
purchased an AquaClear three way filter. Rather than one carbon filter, it
holds a sponge, then a carbon bag then an ammonia absorption bag. My filter
works on tanks up to 30 gallons, and doesn't cost any more than the standard
filters found in chain stores like Walmart. I also bought "Cycle" and
followed the directions for introducing that to the water.

At first the water went green, but then I decided to empty the entire tank
and start all over again. I don't know why, but within two days my fish had
ICK, which I treated them for, however, the water stayed clear. The fish
recovered almost immediately and now I'm enjoying watching them through
clear water. I also replaced the sponge only when I cleaned the tank. You
only replace one of the three components approximately once a month.

I don't know how and why the tank is suddenly clear, but it is a pleasure
not to have to change the water so often.

You can find this kind of filter in a Pet Valu store or any good pet store
that has a good inventory of filters.

Tispe
"Steve" wrote in message
news:OKTde.20500$0X6.8869@edtnps90...
Whats a good filter and pump to buy for a 10-20 gallon
fish tank to keep the water clean for 2 Goldfish. Very new
at this i just got 2 goldfish for my son about 6 months ago
and they are growing very fast. The plastic tank i have is only
3 gallons and the people at the pet store said they would grow
into it and that would be fine. One thing i have noticed is the water
does not stay clean very long and i am changing a third of the water
every 10 days or so. I have not got the tank yet but the size i was
looking for is 10-20 gallons is this ok.
Thanks Everyone for any help.
Steve!