I would say those fish are either sick or being starved to death. Are you watching them consume food? If theyre not interested in food.. then I would treat with general cure very carefully. I feel like those fish are close to death.
Heres a pic I found of someone else's platy fish that had a...
The new aquarium co-op high flow sponge filters are the best on the market. You never have to clean them (for the most part) and they are super effective. I highly advise!
I don't mean to dig up a super old post but... i'm trying to research this topic!? I have a tv stand that looks exactly like this... do you guys think it's strong enough??
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Sounds like you may be rinsing the beneficial bacteria off your filter pad. Stop rinsing them so often. Only clean the pad if it the current is slowed down in filter. It will do much better.
The most common things wrong with betta tanks are:
1. water temp - needs to be 78F minimum
2. cycling...
If your nitrates are 100 ppm your fish are going to die. you need to keep nitrates under 40ppm or your fish will die. You need to do water changes to bring that down.
something is not right with your water. Cycling issues most likely
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To be completely honest.. gourami fish are pretty weak fish are known to have this stuff happen. Not a lot of people talk about it because it SUCKS that these fish suffer through this and die. Here is a link that may help you http//gourami-fish.com/swimbladder-issues