My betta seems Aggressive betta

[funnyskin]

i have a 125 liter tank, with 4 albino glowlight tetras, 1 albino shark, 6 sunset platys, and a Siamese fighter. All seemed fine up and till this week. iv lost 4 of the platys unknown reasons water chemistry is fine, and also seen a demolished shell of one of the glowlights, the fighter seems really aggressive towards everything he keeps flaring (not towards the shark though) what should i do?

[Perseusmom]

Get him his own tank and put him in there all by himself !

[NyaNyanNaa]

Your betta is probably under alot of stress from the shark and that fish would probably even EAT the betta! Take him out immediately.

[funnyskin]

The betta looks like the most dominant in there, and the shark and the betta dont take any notice of each other, and the betta is bigger, i do have a small tank but no heater and its pretty cold round here

[NorthernLights]

Your fish may be aggressive toward other fish because Bettas are territorial (solitary) fish. It's not impossible to keeps bettas with other kinds of fish, but not all bettas are suitable for tank mates.

I am slightly concerned by your referring to this fish as a Siamese Fighter. There are bettas bred for and sold as specifically fighters, and I dearly hope that is not what you have in mind for your fish.

Is it not feasible for you to obtain a heater for your other fish tank?

[funnyskin]

Thats what they were called in the LFS and thats what they are called in 'pets at home' i have no intention of fish fighting and i am just trying maintain a happy community thats why i am seeking advice, and no i can not get a heater at this time of night but it is a priority so will be able to sort one after work tomorrow, but until then no.

[NorthernLights]

Ok, just checking. Sorry, but there are some folks on here who keep fish for fighting...needless to say, my opinion of any kind of animal fighting for entertainment is very low.

So the question IIUC, is your betta better off alone in an unheated tank for the next 24-48 hours, or will your community be okay with him in there for the next 24-48 hours?

Given that a number of your fish suddenly died after you introduced the betta, it sounds like there may be something in the tank. Maybe it came with the betta, maybe it was already at work in the tank. Either way is a gamble.

Do you have a heating pad (the kind people use) that you could maybe stick the other tank on top of?

[funnyskin]

Fairplay dont blame you i totally agree. Been hunting round for something but i havnt got anything, i have got a breeding net but i think that would stress him out, so think im gonna have to risk it. Thers no obvious signs i have anything, what should i be looking for ?