Check your water first. Period....end of discussion. Do NOTHING else before you do this.
You might be surprised at what you find, if you have no fish (or extremely ligh bio-load). I've had situations where tanks sat for a while in the absence of feeding fish (and the waste they produce) that have dropped nitrate levels from incredibly high down to literally nothing with absolutely no action on my part. For example, I keep a bunch of rubble rock in old salt buckets in my garage. I use them to attach frags to since I despise plugs, etc (people love my frags when they are growing on live rock instead of a fake plug). All I do for these, is provide them with an air stone and light....that's all. Sometimes, when I add the rubble right after shipping, the nitrates will jump to deadly levels (after the ammonia spikes, etc). A month or so later and the water is actually absolutely perfect! Perhaps a little low on pH or alkalinity, the the REAL important levels (toxic levels such as nitrate, ammonia and nitrite) are absolute zero.
On the other hand......I've had customers over the years, who had excessively high nitrates, and they have water changed until they are blue in the face and their nitrates are still unacceptabel (even in the absence of fish). This is because (though it's a bit more complicated than this) they have caclum-based substrates which can hold on to enormous quantites of nitrate-nitrogen (nitrates as we measure them typically). As you reduce the level of nitrate-nitrogen in the water column, the calcium-based substrate will begin to chemically release (leach out) that nitrate into the water (which has a lower concentration of nitrate than that which is being held in the substrate). The end result is that the water will come into equilibrium with the amount of nitrate that can be saturated within BOTH the substrate AND the water (anything with a dangling oxygen molecule unfortunately). So, you might water change, and water change and water change, and your nitrates keep going right back up....sigh!
So.....given the results of your water tests (mainly your NITRATE results IMHO), you might be in great shape, or BAD shape. Your nitrates will tell.
Test....the re-post your results. Then we can give you some more appropriate suggestions.
Best of luck and God bless!