All ponds with fish in need a pump and filter, but I don't think this one is appropriate for fish as it's not wide or deep enough.

They'll just drown and foul the water.

You're very welcome. The tank looks lovely and I'm sure he'll be very happy in there

Hi

I've just been reading back over your posts and realised your Betta is currently in a filterless bowl on which you're doing partial daily water changes to control ammonia. In this case, rather than cycling the new filter/tank with ammonia I would move the Betta in and let him cycle it. You'll need to do daily water changes to control ammonia/nitrite while the tank cycles, but you're doing that anyway so overall he'd be better off in the new tank as he'd have more space and water circulation.

That looks more like some kind of tumour to me in which case there's nothing you can do. You may want to try either Esha 2000 or Waterlife Myxazin in case it's bacterial.

Male guppies are randy little devils and will chase anything they think might possibly be female. There's not much you can do to stop them I'm afraid.

The fish food method is unreliable as food resists breaking down (it's designed that way). Switch to household ammonia which can be dosed accurately and immediately.

Short answer to this one - yes, but change part of the water several times over the day to keep ammonia low.

Nitrate is the final product of the cycle and is not processed by the filter, so no matter what size filter you have, nitrate will always rise relative to the number of fish, amount fed, etc. It can only be controlled by watr=er changes, but as a lot of the UK has nitrate in the water supply, it will never be lower than the amount you have from the tap. I would do another water change of about 50% to get it down and then increase your regular changes to 25% per week.

They appear to have either a bacterial or fungal infection - can't see which from the photos. It doesn't matter though as I would advise treating the tank with Esha 2000 which will deal with either.