Goldfish Tank problem

Deank

Help appreciated,
I've a small tank with 3 goldfish in it with a filter, fish are about 3 years old and are healthy, prob is that lately the tank has been getting really dirty and has got to the stage where I have to clean it nearly every 2 weeks.

I changed the stones and boiled the tank late last week to try and remove all bacteria, roll on a few days later and the water is clouding over again, the filter has been changed, as it is regularly, and the fish are not over fed.

Any help would be appreciated, btw the tank is the perfect size for the 3 fish, the are not over crowded.

Cheers,
D

Silverfish

How many litres is the tank? Goldfish need large tanks, common goldfish grow to about a foot long, fancy goldfish grow to 8 or 9 inches.

The water is clouding over as when you changed the filter, you get rid of the bacteria that break down the waste - converting the toxic ammonia produced by the fish to nitrite, and then to less toxic nitrate.
When you remove the filter and the stones, you remove the necessary bacteria.

Goldfish need water changes of at least 25% weekly, and if they are in a tank that's too small, they need even larger changes.

Sleepy

Read the 'Cycling a Tank' sticky: you're accidentally killing all the good bacteria by over-cleaning the tank.

Deank

Thanks all for the advice, I'm not too sure of the size of the tank or what it holds, image below
http://dl.dropbox.com/u/7031476/IMAG0211.jpg

Perhaps they are getting too big for the tank?

I'll keep changing a quarter of the water weekly and see if that improves the situation.

D

Sleepy

Afraid to say they're *WAY* too big for the tank. A goldfish requires an 140l tank, three should ideally have a tank of 220l. The volume of that tank is somewhere around 10l - 15l.

Don't feel too bad about it, most fishkeepers have been in the same boat: petshops sell bowls that are *FAR* too small for goldfish and offer them as such.

You can get away with slightly smaller than recommended tank sizes when the fish are young, I personally have two goldfish in an 100l tank but it requires a lot of extra water changes and care, and will, at some point become too small for the fish (common goldfish grow to over a foot in length, the popular misconception that they only grow to the size of their tank is only true in that too-small tanks leave them stunted and unhealthy and will eventually kill them as their internal organs continue to grow while their body doesn't.

Deank

Thanks Sleepy,
How much would a 220L tank cost, not sure I could afford one.

Thanks,
D

Sleepy

You'd get away with anything over 100 litres as long as you do plenty of water changes and have a large enough filter. New, you'd be looking at a couple of hundred euros but scour adverts and you should be able to get something suitable for one / one-fifty or so...