Fin shreading

[ChimpAndy]

I have a cycled 167L aquarium that I have slowly been stocking. The first fish I added were 6 red phantome tetras. I've since added 3 ottos, a pleco and a couple of snails. Over the last week I've noticed a couple of the tetras starting to fight. I assumed this was males fighting to be top dog and hoped it would settle. I've noticed today though that 1 fish seems to be coming out worse and it's fins are getting quite shredded. Another fish has a single split in its fin. I'm now concerned however that this could be fin rot? I've checked my water quality and I have no amonia, nitrite or nitrates. Water temperature is currently 23.8 degrees. PH is 7 and the water is hard. If this is fin rot, what's the best way to treat it? I have 2 snails and cherry shrimp in the tank so it needs to be safe for these. If its just aggression related, would getting a few more tetras help? I'd planed on adding a few rams next which would also encourage the tetras to shoal more.

Thanks for your help
Chimp

[black ghost]

It’s not finrot, and yes increasing the numbers should help. You may have too many males and not enough females.

Can I also say you need a lot more Otos for them to get unstressed. I say a minimum of a dozen for Otos, since they live in huge ‘herds’ in the hundreds and sometimes thousands. They’re very stressed in small numbers.

And Rams are not suited to your tank. They need a temperature of 80+ which your other fish won’t like. And they don’t like hard water.