My 2.5 is over three years old now, but has been rearranged a couple of times due to overgrowth of vermetid snails, hydroids, "tulip anemones", corals that got too big...etc. In these small spaces, you have to account for growth, and some organisms like vermetids and hydroids can grow and spread very quickly. Vermetids and hydroids, left to grow to trememdous proportions tend to irritate and/or kill nearby corals. I prefer my corals to nuisance organisms, so I choose to remove and replace any pieces of LR that have too many vermetids on them. Haven't had any issues with hydroids or those annoying "tulip anemones" that I had at one time, since removing those two years ago.