How long has the aquarium been set up. Whats your nitrate reading? What are the other species of fish? How many gallons is the aquarium?

Gourami,betta,platy… Nitrate readng dnt know new to these…

Betta’s are aggressive and will kill most fish.  I don’t know much about Gourami, but I believe they can also be agressive which may be why the betta hasn’t killed them yet, however if your Gourami are bright colors they could be next.

Also, should get a water testing kit. Very important to test water levels. If they are out of wack, fish will die.

Seperate him, get a small tank.  You can keep them in a betta tank.  They are just tiny and I feel bad for them in there.

The beta wont kill fish its more than likely due to the aquarium being new and the mollies are just the first to go being the most sensitive to the ammonia (fish poop).

Yes its true they will attack fish with flashy fins. For an example mine would bit off my high finned platies top fin (it was red and large) when it grew back he did it again. They want to be the best looking fish in there lol He did that in our 20 gallon, when I upgraded to a 46 he couldnt catch him anymore lol. Thats how bettas end up killing each other when they do fight. They bit off each others fins trying to make them not as pretty. In the process it can kill the other fish or just make it hard to swim or of coarse lead to infections with so many wounds. In nature I doubt they really kill each other since they have the option to leave. In an aquarium they dont get that option.Its a great starter fish to cycle your aquarium with. They are hardy and will probably out survive the other fish. If you end up with just one fish just keep it that way until the cycle is finished.

gourami also agressive molly are weak among your fish nxt one will die is your platy if u dont separete the gourami ang betta from it.

She is right about why a beta will injure another fish or possibly kill it. But I would still take the beta out so that doesn’t happen. Mollies are a much weaker fish than betas are. Plus side when you have to separate, betas don’t require that much attention.

We’ll my female Mollie who had babies last month just up and died yesterday. I don’t have  another female of her  kind in tank either.

I was having baloon molly… She gave birth to 57’babies… And died after 3 days…. Fry I gave it to aquarium shop owner in exchange of pair of baloon molly…

How long have you had it set up with fish? The deaths may be caused by the cycling process. During this time the fish’s waste is toxic to them. It usually takes about 4-8 weeks to finish and good bacteria living in your filter to be able to break down the fish poop so its not toxic.

Ok so its the fish’s poop killing them in very simple terms. You need a water test kit (if not affordable bring a water sample to the pet store they usually do it free) You need to get a gravel vacuum though and start the water changes. It looks like this…

Remove about 20% of the water from the rocks (suck the poo ect right out with this into a bucket) Water changes in the first few months need to be done weekly.

Dont replace any fish until your water reads 0 ammonia (goes up and comes back down as good bacteria grows) 0 Nitrite (also goes up and comes back down) Nitrate should eventually read 10-20 ppm. This will show your aquarium is ready to break down the fish poop on its own and you can do less water changes if you choose. Before this is complete its up to you to keep the ammonia level down with water changes. After the cycle is done the nitrates need to be removed but are not as toxic as the first stage of fish poop (ammonia).

Even though the good bacteria can convert the ammonia to nitrates on its own after a few months you still have to do the water changes because even nitrates at high levels is toxic. With water changes you keep it around 10-20ppm and the fish can tolerate it at low levels

I like this as a visual to try to understand how it works. Its definately a learning process so just ask any questions even if you think they are silly. We have all had them… I had to learn this before the internet and have no idea how my fish survived

Just share my mollies with a betta fish on the upper right corner, shes just ignoring the mollies even the mollies r agressive when it comes to feeding they were fast cathing the food ive given.

All of a sudden my fish are dying! Including my favorite Black Sailfin male molly 😥. I have a 10 gallon and a 20 gallon tank and when I test the water everything comes back normal. Nitrates and nitrites are at zero, PH has always been good and my water is brackish… I can’t see any signs of illness besides their behavior so im assuming it’s an internal parasite or something? The 10 gallon tank is fine. I’m having issues with my 20 gallon. The females are being VERY aggressive towards each other all of a sudden, two have their fins clamped, and one seems to be having a seizure…? What are possible illnesses to cause four deaths in 24 hours???

Did you add any new fish in? There are many dieases that can kill over night sadly. What other fish were in the tank? And what was the salt levels?

No I haven’t added any new fish. I have 7 MollIes and 1 gourami in my 20 gallon and its the only tank I’m having issues with. (I have 3 tanks) The salt levels were normal. GH was between 60-120 and KH was between 80-120. I have the 5-1 test strips and get my water tested at petsmart every couple of weeks…the only thing I can think of is some kind of disease or parasite but I can’t figure out what it is or how to treat it.

If your nitrates are reading zero that means its not cycled. What is your ammonia reading at? That could be high stressing everyone out.

Don’t clamped fins usually mean there’s a toxin present?  Is there any chance you came into contact with soap while cleaning the tank?  Just throwing out guesses.  Hope it gets better!!

They seem to be doing fine now. I was told to turn up the heat for a few days to quicken the life cycle of bacteria and parasites then fed them crushed peas. I guess it worked for now. Thanks!!!

Clamped fins means they are stressed. For many reasons…It could be from toxins, inner and outer parasites or bacteria, bad water parameters…