Plain and simple, do t add livestock to solve issues. Once it's solved, it's an animal that will need to be fed.
That said, you created the current issue with the tap water. The original goings on was diatoms. Simple silicate consumer. Then you moved into Cyanobacteria and then into hair algae. These last 2 are indicators of parameter issues, be it nitrates or phosphates. At the amount you describe, you won't even be able to test for them anymore.
The solution is large water changes with ro
/du water and manual removal of the algae. It will take time, as even nitrates of 50 will only go down to 25 with a 50% water change and the begin to rise until the next water change.
Do not use tap water. You are just adding nitrates or phosphates into your water column.