Hi I have a small pond in my garden for wildlife it it about 60-70 liters it currently has 1 frog which has lived in it for about a year there is no filtration so it it a bit green anyway I was wondering what fish could go in it to give it a bit more life maybe wcmm I do tiny water changes on it each day because I empty the guinea pigs water bottles in it which is about 1 litre of clean water added a day I could also do lots of cleanouts but I can't add filtration because there's no plug so what small fish could live in it that could preferably breed incase the frog eats some