I would actually replace it with a True Actinic bulb. All of our T5 fixtures at the shop only have blue plus and true actinic bulbs.
What would be your 8 bulb Combination?
6 B+
2 True Actinic
That is my ideal mix for an 8 bulb. If you like the tank a little whiter I'd change out a B+ for a Coral Plus
What slot should I put the 2 true actinic
Front to back I would do this layout. So atleast 1 actinic is always on.
B+
Actinic
B+
B+
Actinic
B+
B+
B+