Hi there,

We have a tank with 2 gold fish and 2 small cleaner fish in (50+ litre tank with pump and filter etc).

We have checked the chemicals/acidity of the water etc but they both seem not be swimming around so much for the last couple of weeks (have had them for maybe 6 months and theyalways use to swim around a lot).

I am feeding them a pinch of food each night (takes a couple of mins for them to eat) and I clean the tank, replace 20% of the water and change the filter every 2 weeks.

I did have some living plants for a few days when we first got them but they started to float around everywhere so got rid of them and assumed that the water would get oxygen in it from the water running back into the tank.

Cheers Mark.

Do not change the filter, just rinse it out with mature tank water not tap water water otherwise you will destroy the nitrogen cycle resulting in your filter being useless. A few plants will do no harm but are not necessary as long as you give them a balanced food that contains vegetable matter, I use the odd slice of cucumber in my coldwater fish which they appreciate.

50l is to small for 2 Goldfish - it's too small for 1. To be honest, goldfish belong in ponds not tanks. A full grown goldfish can be 12 inches and live to 15 years.With insufficient room the fish become stunted. This and you changing the filter is probably the problem - the filter serves two purposes - it physically filters out particles from the water and, more importantly, the bacteria colony that live on it break down the ammonia that your fish produce. Replace that and the colony has to re-establish each time which takes a minimum of 2 weeks.

If you can rehome your goldfish to someone with a pond that would be the best for them, otherwise you need a significantly larger tank - 500lt minimum with double filtration.

50lt isn't really suitable for anything - you might manage a small shoal (6) of white cloud mountain minnows.

Don't feel bad though - I think almost everyone who has kept fish make the same mistake

Thanks for the replies.

I thought the tank would be more than enough size after looking on the Internet along with a lot of other people we know having 20 liter tanks.

I will try washing the filter out as do not have the space for a massive tank and once these fish and go maybe get some terepins.

I'm not sure terrepins are easy to keep, are they?
The best fish for a small tank imho are siamese fighters - though you can only have one male. I'd look into that as they are very pretty and there's a massive fanbase out there who will have plenty of tips on keeping them and suitable tankmates for a tank your size.

Terrapins can get 12 inches or so as well, and are very messy. They would preferably need an indoor pond. Research Reeves Turtles, they stay much smaller, and are much more manageable.

Edit: didn't see your tank size, even Reeves Turtles need around 20 gallons, so maybe a Siamese Fighting Fish, or some Celestial Pearl Danios would be more suited.

Are you sure you don't mean 20 gallon?
20 litres is tiny.
Gold fish are huge poopers, so they need large water areas. They're not really suitable to tanks unfortunately, as the ammonia they produce is toxic and they would need constant water changes.