Hi, you can visit to this forum : http://www.aquaticquotient.com/forum/
For me, this forum is ideal for planted tank. There is LFS directory in that forum also. You can check it out.
Yea, relay is needed to isolate power supply from float switch and supply for the pump to get the stable current flow to the float switch. Those float switch need stable current to maintain their lifetime. Just my 2 cent knowledge.