Okay thank you for answering my questions , if you cannot answer , thank you for reading , here is My problem.

I have a betta and 2 corydoras in a 30cm tank , yup a pretty small size , a 3 gallon , but the betta bite the corydoras so i have to separate the tank into 2 , which makes it an even smaller size.

I am thinking of upgrading it into a 60cm tank , but it would be boring to see only a betta and 2 corydoras , are there any tank mates that i can add ? Is harlequin rasboras suitable ? and lastly , is it okay that my 60cm tank wont have any light due to a limited budget?

Thank you for answering , and reading

I'm assuming that since 60cm is double what you have now, it will be a 6 gallon tank. In this case no, you can really only have the Betta and maybe a snail and possibly a shrimp or two... but the Betta may eat them.

Cory Cats are a schooling fish and need to be in a group of 5+ (you may be able to squeak by with 3), but in your tank, I don't think it would be good to add anymore fish. I'd re-home them or trade them in. Then, put the Betta in the new 6 gallon tank and add a snail or two. Live plants will help spruce it up a bit, but you will have to get a light if you go with live plants.

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Your tank is way too small. If you want a lot of fish just go for a much bigger tank.

Just like Holly said, a six gallon can house a betta and couple snails, but not much else unless you want problems.

You would only need light if you're keeping live plants which makes your tank nicer.

You should probably read on the nitrogen cycle, fishless cycling and drip acclimation too.

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60ltrs will be about 15 gal. You could add a bunch of silk plants that won't hurt the bettas fins and add a couple more cories. I don't know if I would add rasboras to the tank, you might want to find something a little larger. Maybe a couple of platies or swordtails.

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220 Tank build
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I think it wouldn't hurt if you posted all the dimensions to the tank so, we can find out for sure how much water can fit in there.

length, depth and height.. is all that is needed..

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Current : 30cm(L) / 20cm(W) / 20cm(H)
I am thinking of upgrading it to 60cm(L) / 25cm(W) / 25cm (H)

Thanks for all the replies btw Appreciate it .

With those measurements it comes at around 9.9 gallons... so it's a ten gallon tank..

With the gravel my guess is that you have 8-9 gallons. In that case, I don't suggest you get anything other than a betta and a couple snails in there, otherwise you'll have stocking issues. Both Corys and Rasboras need to school so you need 5 or more..

Platys do well in ten gallons... Swordtails are longer so I don't recommend them. Plus you have to see your Betta's temperament. While those fish are suitable tankmates for a Betta, the Betta can still go postal on them.

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And sorry to bother , one last question , do i need a heater ? i live in a tropical climate.

I think it would be wise for your to get a heater and thermometer. Bettas prefer a temperature of 80 degrees. Not sure about the other tankmates, I think Platys prefer a little less than 80... but I don't know if they can handle 80 degrees. I think if you keep the water at 77 degrees it will be suitable for both.

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Betta's like temps' in the 80's, so if your water won't stay that warm by itself then you will need a heater.

I agree with Pigeon - anything other than a Betta and some snails in a 10g and you will have problems... I had a 10g and tried many different stocking options and was always running into trouble. Finally up graded to a 20g for those fish. Also got a 36g so I could get some different fish that need a different temp'.

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