Hello all fish hobbyists,

I have recently bought a 40L tank and got it set it 1 week ago and just added 6 Cardinal Tetra's (3cm each). I was hoping to add in 2 Dwarf Gourami's (4cm each) and 2 Cory catfish (4cm). In the pet store I bought everything from they said I would manage with that. After some research I'm thinking that might be slightly overcrowded and cause the water condition to deteriorate quickly after each change.

Can someone enlighten me if that would be overcrowded or it would be good living conditions for the little guys? I have all the water treatments to add in; Tapsafe, Filter booster, Ammonia remover & plant fertiliser for the 2 real medium sized plants I have. There is also 3 moss balls to help oxygenate the water.

Thanks

You're quite correct in that a shoal of 6 cardinal tetras, 2 dwarf gourami and some cory catfish (which need to be kept in a shoal of 6+) would overcrowd a 40-litre tank. Even the cardinal tetras alone really need a tank of a 60x30cm footprint minimum.

I would stick with what you have, and use the info from the following for advice https://www.fishkeeping.co.uk/modules/ ... resheet.php?caresheetID=1 and https://www.seriouslyfish.com/species/paracheirodon-axelrodi/

As you're doing a fish-in cycle, then it would definitely be worth buying a liquid-based test kit for measuring ammonia, nitrite and nitrates daily for the next couple of months and following the advice in this if/when required https://www.fishkeeping.co.uk/articles ... ammonia-nitrite-spike.htm

Yeah I thought that, I guess the pet store were trying to sell more than was safe! They knew what tank I had etc. I think it'll be okay to add the 2 Dwarf Gourami's and leave the cory's unfortunately. Should've gotten a bigger tank but didnt want to go overboard with my first one.

I've already got the testing kits, testing the water weekly.

Cheers!

The tank is too small for dwarf gouramis - the minimum for that species is 60 litres. Their adult size is much bigger than 4cm; more like 7-8 cm for the male and 6-7cm for the female.

Well thats bad news right there, the people in the pet store have told me a load of baloney then! Not happy at all. Guess ill have to reconsider what smaller fish to add that wont overcrowd the tank.. any suggestions?

https://www.fishkeepingworld.com/dwarf-gourami/

says here a 10 gallon tank (45L) could house 2 or 3 Gourami's

Most website differ and contradict each other that I've been researching. Just want to make sure the fish will be happy and heathy.

That's an American site and the standard of welfare for fish in the USA is not as good as UK and Europe. We recommend either using the care sheets on this site where available or, this site which is highly regarded by many in the hobby and has accurate, well-researched data for hundreds of species: https://seriouslyfish.com/knowledge-base/

The sparkling gourami is smaller (and a lot healthier) than the dwarf gourami and would be suitable for your tank size: https://www.seriouslyfish.com/species/trichopsis-pumila/

Thank you very much for the help mate, ill have a surf through that website today and do some research.
Happy fish keeping!