some people use rock as their main filtration others will use a sump, or HOB or canister its personal preference. Best way to cycle the tank is to get a few pieces of LIVE ROCK, this rock carries the bacteria needed and will help to cycle the tank. Also feeding the tank (adding a source of ammonia) is another great way, some use fish but it can be very stressfull on fish and there for more don't. I'm not an expert but i'm pretty sure its a bad idea to mix seahorses and pipefish