[No powerheads, single pump for maintenance, only a single plug needed, etc.
Just about any plastic paint will work, but it has to completely dry. Even when it feels dry it may not be. I'd give it a week. Most of the poisonous things in paint evaporate out.
Other options would be:
-use black, grey, or clear PVC.
-put many coats of purple PVC primer on it
- coat it in a small amount of silicone and roll it in LR rubble or sand and let dry.
-wait a couple months and let it cover with coralline.]