I used a shop light over mine along with my coralife FW aqualite and my plants grew pretty good. The shop lights are fine, but keep in mine that they don't come with a good reflector. Basically you’re going to lose quite a bit of light because its not focused into your tank. However using two sets of the shop light over your 55gal is better than nothing. Just upgrade whenever you get the chance. Till then you may look at creating your own reflector using mylar or something (just do not use aluminum).