You could just have the live rock and use that as your primary filtration. As I said a protein skimmer is also necessary, helpful but not necessary. So you are not having to purchase a mechanical filter but you will need power heads to agitate the surface and creat water movement. I know it sounds expensive for rock! Some people use dead or dry rock and it will eventually become live over time if you need to save some costs. Unfortunately salt water isn't cheap! It takes time and money to start but I can tell you it is much more rewarding than fresh!!! You will also need a salt water test kit, a refractometer (for measuring salinity) and a good water source like a ro
system. No tap water I am afraid. You can buy pre made salt water and ro
water from LFS
but of course the costs of that add up...
Then further down the track you may want to invest in corals or anemones and they require intense lighting which can be very expensive! Does that help?