Thank you very much
Yes you can move then easily, the problem is to have them stay in place . Sometimes they do other times not. The easiest solution is to use fishing line, or elastic bands to fasten them.
Im not sure. It depends on what's actually in the phytoplankton. Maybe a good idea is to stop using it for a while and see. What I would suggest is the recipe for home made food. If you follow the directions and use it I think you'll find it better for your tank than anything you would buy pre made. definitely try it. It very inexpensive and is remarkable.
Let me know the results if you use the recipe. Robert