In the axolotl tank, which has the algae, I never added any leaves nor meds, because they have to be treated differently to fish. Example, being pulled out of the tank and put into a bucket or even at times a fridge and treated.
In their tank, they have a few water plants, a plant living on drift wood, a filter and heater and also some air. I've also having an issue with very thin, small white worms in the tank and lice like things on the glass - though they aren't lice just look like it. I think I'm getting them from the plants I'm buying as I've had the lice things before and they grew into bigger, fatter worm like things. I've so had the thin worms in another tank years back that had plants.
I use rain water in all my tanks so I don't even use water conditioner.
I only just added some leaves to the tank I had as a hospital tank for my axolotl, which doesn't have the algae though has had plenty of meds. Very confusing I know. . .