The sand looks like it should make a bed about 1.5" deep so not too much, not too little. Since speaking to the guy at my favourite LFS (bloody brilliant shop) he has recommended using Marine Pure Ceramic balls, some sponge and Chemi-Pure Elite in the canister with the Hydor Koralia that does 225GPH (900LPH).That's plenty of rock and sand. Depending on the dimensions of the tank, you may not need all of the sand.
Not familiar with Marine Pure but from their website, it appears to be a ceramic media for housing nitrifying bacteria. If that is the case, it probably won't provide much benefit over the live rock which does the same thing on a larger scale. What you need is something for phosphate and nitrate control. GFO water changes will help phosphate but nitrates are a different animal.
Nitrate's conversion to nitrogen gas is the last step in the nitrogen cycle and it requires a different type of bacteria than those that convert ammonia to nitrite. Denitifying versus nitrifying. Denitrifying bacteria that convert nitrate to gas grow in anerobic (no oxygen) conditions. If your live rock has deep enough pores, you may get some denitrifying bacteria from that. However, it is tyically not enough to eliminate nitrate altogether. Nitrate control is best handled by one or more of the following. The top 4 are key IMO:
-Avoid overstocking fish
-Avoid overfeeding. Also drain/rinse frozen foods.
-Regular water changes (I would definitely recommend weekly 10 to 20% changes without a skimmer)
-Using a good protein skimmer (won't remove nitrates altogether but will help greatly)
-Macro algaes (not really a viable option without a decent sized sump)
-Using a deep sand bed (minimum 6") (also not really a viable option without a sump)
Okay, so I'm thinking 15-20% W/C every week and cleaning the sponge in the canister every week with a whole canister clean every 3 weeks. That in combination with the Chemi-Pure Elite should keep nitrates to a minimum.
Stocking wise, I know I want a clown (who doesn't?) and a few turbo snails, maybe a shrimp and maybe something colourful that'll scoot around on the sand and rocks and look funky like a goby or hawkfish or something as well as the soft corals. Opinions on that?