Not a member of LARK so hopefully I can avoid the firing squad. I keep posting here but you guys/gals keep posting interesting things
No, you don't fill it all the way up. You want it to tumble the media but not rolling like a boiling pot. If its too fast, then it simply grinds the media down too fast. If its too slow, the media will clump and can't do its job.
If it gets out of the reactor, it won't hurt anything other than maybe giving a rust colored tint to the water that Carbon will clear up.
How often you replace it depends on how much phosphate you have in your tank and how much its pulling out of the system. Sorry, there is no solid answer to that question. Its something that you kind of have to figure out for your particular tank. A tank without a sandbed will use up phosban quicker than the same tank with a sandbed. Feeding habits will also affect how long it lasts. A lot of other things that have an impact on how long it lasts so thats why you can't say "replace it every X months".
HTH and please don't shoot me TOO many times
