I definitely would add 3 to 4 times the water volume. I had one at about 125 gallons and it was never stable. Do not cheap out on the protein skimmer, Get one that is rated for twice the volume and a reliable brand. IE: Euro-Reef or Deltec. With out the Live rock you will need this big skimmer and you will be thankful you did it. Next try to use the true Poly filter fiber, it is the best for pulling organics and pollutants out of the water. the filter floss and off brands will not do the job. Try to run this as on of the lst parts of the filteration. Running Charcoal/Carbon and a filter sock (not together) would be reccommended too. Also running with out the live rock, load it up with Bio Balls, You will have to have the surface area to grow the bacteria needed supply the system. On another note, stay away from the horseshoe crab and fish. Most people will get cut or poked and start to bleed in the water.