4ft flouroes

my plants need more light and i was woundering if i could add some 4ft floroes to my 400 watt hps and would it make any diffrence and if yes what kind of bulb should i use.

Well, adding any light is good. One of my last choices would be the four foot tubes (just opinion) but if you do use them then get the high output t-5 tubes.

High Output Fluorescent Plant Grow Light Systems, Bulbs & Accessories at Home Harvest Garden Supply

Yes you can use 4' tube fluros to surround the plant with side lighting. Stand them up vertically & use whatever bulb is necessary for your stage of growth like blue for veg. or red for flowering. U could also use CFL around the sides which may perform better.

i say its pointless