Well as the questions says how old does a fish need to be to spawn

The reason for the question is that i am not 100% sure but i may of had one try to spawn or was it just going mad as the fish have been in the growing on tank for about the same time nearly a year and there have been no more addition or any changes. The only thing that has changed is last week the pump went so i had to put a new one on and did so but increased the pump from 12000 to a 15000.
I went out last night and was having a look as they are all looking good and switched the air pump of to the tank and forgot to turn it back on but have done this before without problems. I went out a while later and the tank was full of foam and some of it had brown stuff on it but i couldn't see eggs as such and there was water everywhere on the walls windows door ceiling the lot


I then had a good look in the tank and one of the Mukashi was bashed up i think it looks like every fin is split apart the anal fin


Will keep an eye on them and see how it goes with the fins as there may be some treatment needed