Why not?? In the reptile world, those pet owners never have to clean waste. There are bugs that clean for them. I don't understand why it can't be that way in the fishkeeping world. Why there isn't some aquatic animal that can added to replace fish tank maintenance. I already know to keep my water parameters cause any fish can die from poor water quality. You said they filter algae, so they shouldn't starve. I have algae growth in my tank.
Please take this as it is intended, to help you not only solve a problem but understand the issues behind these.
There is absolutely no replacement for maintenance of an aquarium by the aquarist. None. That is not how nature works. In the wild, there is a system that has evolved over thousands of years to maintain various species and along the way help them overcome various obstacles. [I don't really know how to better express this, so I hope it is understandable.] "Problem algae" does not really exist in nature, because each habitat has what has evolved to function there; if algae proliferates, fine, it will choke out the plants. In another habitat the botanical needs of plants will be provided and algae will be non-existent, as a hindrance at any rate. There are all sorts of checks and balances in biology, botany, chemistry to ensure this is successful.
In an aquarium we introduce various species of fish and plant, so the natural life processes play out for each species. But the aquarium is a very artificial environment, that does not exist anywhere in the natural world. We confine the species to a space where some of the natural processes cannot play out due to space, light, temperature, combinations of species, etc. The aquarist has to learn what the processes are, and what environmental factors are necessary for each species, but the course some of these take is far different.
Algae in an aquarium is normal; light plus nutrients will cause algae to appear. There is no such thing as an algae-free aquarium; those photos of such tanks are phoney. Such an aquarium is unhealthy because what is necessary because of nature is being eliminated, or at least the aquarist attempts to eliminate them.
There are some who deny the need for water changes; they may cite tanks with plants that run for years with no water changes. These people have no clue about nature. Even Diana Walstad who instigated the soil substrate method admits in her book and articles that she only gets away with minimal or no water changes if the fish load is considerably lower than most of us would have, and the plants are heavy and thriving. And no plant additives are added. The fish produce the nutrients the plants use, and it is in balance. I recall reading some years ago that a planted aquarium with fish that received no water changes could only work if the fish load consisted of six black neon tetras in a 55 gallon tank well planted. I doubt anyone onthis forum wold keep no more than six small fish in a 4-foot 55g tank. It takes maintenance to maintain a healthy aquarium.
Fish that do eat "algae" will usually not eat the "problem" algae we have to deal with because we do not have the biological system balanced. I've no idea about clams, but this is not in my view the way to go. Establish the balance of light and nutrients for the plants you have, and I can guarantee you will never see "problem" algae. It took me a few years to do this in my fish room, where I had problems with black brush algae in two or three tanks. Once I achieved the balance, for the following six years I never had this algae increasing.
Snails and shrimp can assist the aquarist, provided the system is in balance (fish load/live plants/water changes/filter cleanings), but they cannot replace maintenance.
