MH and T5 spectrum help

[MJ in Boise]

I've got 2 frag tanks with about 1000 trochus running around. Just pulled the last corals out and would like to get some opinions on bulbs for MORE algae growth. 1 tank has a 400watt 20k radium over it, and the other has a 4ft 6bulb t5 fixture. If I pull the 20k and replace with a 5500 GE 400 watt will I risk some nasties, or will I get more algae growth for the snails? Same question for the T5 fixture, pull the ati bulbs and replace with GE 6500s. Both tanks are connected. System runs 2ppm N, and .01 P. I'll raise these slowly now that the corals are out.
Thanks for the help.

 

[C. Eymann]

Id go with the 5500k for the halide, then
GE 6500k full spectrum T5s

I actually run a GE 6500k T5 in the mix of t5s over my reef.