Johnny the Siporax would be an excellent idea. You have minimal rock. Siporax is just a live rock substitute. It has an insane surface area for bacteria to grow on. There is a huge thread in the SPS forum. There is no dosing, just throw it in there and let it do its thing. Some run in a reactor, but honestly a bunch in a bin or eggcrate box should do. I have a reactor with about 1.5L but then added a few more L and they are just in mesh bags. It doesn't hurt anything and can only help, especially if you are going for a high bioload. Matrix is another similar product and is easier and cheaper to get here.