Goldfish expert opinion request

PoGee

Our fish are around 20 years old. What volume is required for 2 fish 21cm in length?

MattMattMattUK

In theory based on fish stocking level you could get away with a 75 litre tank, however you would be better off getting something in the 100-200 litre range as it would have better width for them to turn in, you could also stock a few smaller fish in the tank as well then.

PoGee

Thanks for reply. They're in 240l. They're on their 4th tank, each getting progressively bigger. They look like they've had another growth spurt so thought I might have to get one bigger again. Nightmare to clean.

MattMattMattUK

PoGee said:

Thanks for reply. They're in 240l. They're on their 4th tank, each getting progressively bigger. They look like they've had another growth spurt so thought I might have to get one bigger again. Nightmare to clean.

Then that tank size is fine. Fish limit growth based on environment, or at least several slow it. Goldfish are a subspecies of carp, keep them in a small tank and they will not grow much, but give them space and they will grow. 

Are there a reasonable amount of living plants in there? Snails? It could well be worth adding some other snammer fish and some cleaner fish, plecos or similar (speak to your local aquarium stockist). It will also depend on the kind of filter you have in place but the algae eating snails and fish will reduce or nearly eliminate the need for glass cleaning, a good filter will reduce a lot of the rest and you can probably use one of those gravel vacuum things to do the small amount of cleaning that will be needed in a well balanced tank when combined with regular water changes.

PoGee

Just invested in a couple of good filters. I tried live plants a few years ago but the fish didn't eat them ( not sure if they are meant to eat them), making the tank slimy. I've seen the electrical gravel cleaner online reasonably priced at £45 so will probably get that also. The gravel is real stone, plants plastic, plenty of hiding places and oxygen via fish tank stones + carbon filters. I must be doing something right for them to be a good age