Why is my betta NOW suddenly territorial?

Question

My previous betta died about a week ago, and I didn't know what caused it. So, I washed out the tank and rinsed the gravel, but kept the plants "dirty". It was only 3 weeks old (the tank I mean) so I'll just have to restart with the cycle. Anyway, I got a new betta in the tank along with 3 mollies. The 3 mollies were in there first, etc and the past 3-4 days they have been perfectly fine together, and now suddenly my betta is flaring up at all of them. Why??

(it's a 10 gallon)

Answer 1

Bettas are actually very friendly fish as long as you don't put two males together. They get along with most other fish, and what you really have to watch out for is the fish that harass bettas.

Bettas are slow moving fish with very long fins, so they can't be kept with any quick fish that have a reputation of fin-nipping, like zebra danios. They get along *great* with most variety of tetras, Mollies and platies and other of that variety also work well.

I've had bad experiences with keeping bettas and guppies, as the male bettas will mistake a male guppy tail for its own sort and fight. Other people do fine with them, though.

No goldfish. Goldfish come from cold water and bettas from very warm water, so their temperature requirements are very far apart, and also their general water conditions. Goldfish are very heavy water pollutants and require an absolute minimum of an inch and a half of fish per gallon of water (the usual way to estimate how many fish in a tank is one inch per gallon).

When mixing bettas in a community tank, the thing to keep in mind with bettas is that they are fish that originally came from very an area with slow moving water. So any type of major filtration on the tank will shock a betta and make him hide in a corner away from the current. You have to balance this with the other fish in the tank that require the current and bubbles for the oxygen in the water for them to live. On the other hand, once a betta gets used to the "current" from a filter, you will sometimes see the betta 'playing' in it for fun. Just make sure that there is a quiet area in the tank for the betta to move to when they are tired.

Answer 2

Your betta thinks that he is in a new tank. And, he first thing fish do when they are in a new place is to take over a piece of the tank.

Answer 3

Most likely this is because a 10 gallon tank is not sufficient space for the betta and 3 mollies. It's really not even sufficient space for the 3 mollies alone. Beyond that, you said you've just re-started the cycle, which means you're going to have some serious problems with that tank real fast. The ammonia will start to be problematic in about a week or so, so I hope you are prepared to do multiple emergency water changes daily for a while, and even then I don't know that your fish are going to survive.

A fishless cycle or a cycle with a couple small hardy fish would have been a better idea than throwing 4 medium sized fish into a 10 gallon tank and waiting to see what happens.

Good luck...

Answer 4

the new betta that you got might be very aggressive towards other species and is determined on defending his territory. it would be better if you get another female or remove from the tank to prevent killing your mollies.

Answer 5

he is trying to be the dominant fish in the tank