seeking beginners advice on water feature fish

Hi everyone
I've perused the threads and haven't found an answer to my exact dilemma so I'm hoping someone can give me advice.
I have a concrete water feature in my garden which consists of 3 staggered bowls (about 30l each) with a pump in the bottom one feeding a fountain in the top one to recycle down again. It's essentially a wonderful mosquito larvae breeding hole. I was wanting to put some fish in the bowls to control the mosquitoes and algae and plant detritus but I'm not sure if it's too small or would be cruel to keep fish in this. I was considering gambusia but know they are aliens or goldfish but don't know if it's too small for them. I don't want to keep fish for the sake of it if they are not going to be happy but like the idea of a micro ecosystem even with supplementary feeding. Please any advice would bexpect most welcome!

 

I think in a tiny 30l bowl gambusia is your best option.
Maybe whiteclouds could work as well,those are not blacklisted.
If you are prepared to heat the water during winter you can try guppies or platies.