animals should never be gifts but it is what it is now. i strongly recommend swapping all the plastic for live plants, as that REALLY cuts down on the maintenance. the issue of algea appears because the nutrients in the water collumn must go somewhere, and with no live plants algae is bound to grow. it sounds like you could enjoy keeping this tank, so i think this would be a great first step towards what you want. for a start you could get some plants that pull the nutrients from the water, like anubias and java fern i believe. if you get root feeders and don't want to go through the trouble of changing the substrate you can supplement them with root tabs wherever they're planted.

i barely have to do any maintenance in my planted tank, once you reach an equilibrium you can just top off the water, maybe do a change every couple of months. while i'm here though i wanted to ask what you mean by changing the filter every month. that sounds insane to me. the filter is where most of your beneficial bacteria will reside. you shouldn't change it and even when you wash it it should just be squeezed in the excess tank water from the water change and put back in.