Your tank looks good. I would also agree with the other posts to change your substrate to a fine granule. Also, may I suggest that you take out the sponges on your powerheads and rinse them out really well at least every week. I had a similar powerhead and all kinds of bad stuff accumulates in the sponge and causes problems. Just a suggestion.
Do you plan on having corals??? and do you plan on having other types of fish in there? If so what kind? - just curious. I also have a 55 gal. I like to see what other people do w/ the same size tank. In hind sight I wish I went with at least a 75 gal because the 55 is IMHO not deep enough to have nice aquascaping and space for fish to rome. Oh well, something to look forward to.