[canadawest]

Patrick, I can offer a contrary opinion. Due to questionable advice and my lack of knowledge early on, I also started my tank with a 1"-2" layer of crushed coral. Granted I got really fine crushed coral, but it's still crushed coral.

I have since added a bag of Caribsea special grade sand, and about 10lbs of dolomite sand over the past year with no consequence. Now I have a mixed sandbed of several different grain sizes which is exactly what Shimek prescribes.

Unless you are using the coarser crushed coral, I see no reason why you should have to remove it all before adding a finer grade sand. The benefit of starting with crushed coral is that the finer grains will eventually work themselves down through the crushed coral without any stiring required and help to achieve the mixed grains that shimek recommends.

And as a side note, I have never had over 5ppm of Nitrates in my tank since the original cycle. With the proper cleanup crew, there is no reason the sand should become a detritus trap, and even though I only have about a 2" sandbed in my tank, I frequently observe nitrogen bubbles escaping.