I have heard to many people that have had problems, and I myself have had this happen twice on tanks I maintanced. The flora base gets into the filter, and gums the impeller and shaft. If not caught within a few days of it happening, the flora base can make one big brick of your impeller. When this happened to me the first time, I didn't even know to check on the filter, and when I was told and did I had one big nasty gnarly brick in the housing. I ended up soaking it in a bleach water 1:1 solution until it became a little easier to work with, but ended up throwing the impeller away and getting a new one. The second time I checked a couple days after the tank was setup, and it was hard, but not to the point of buying a new impeller. I have had great success with eco-complete, but better success with flourite and laterite. Have yet to do the peat moss sub layer.