Reply To: Rain water for seeds and seedlings.

[Cleansweep]

Suggest you paint the tank to exclude light, this will inhibit green algae. To paint the outside with black bitumen (Aquaseal 5, 2 coats). Just mask off a strip “gauge” on the north side to see contents. A filter on the downspout ,such as a surplus sock, to trap debris.The use of non-chlorinated water should prove to be advantageous, so long as the supply is dependable.