Switching to sand

[NETSECPRO]

I have a 29G tank with crushed coral substrate, however I'm starting to think that a sand bottom would look a lot better. Would it be OK to take out all of the crushed coral and replace it with sand?

[ACBlinky]

I'd do it all at once, providing you have enough LR to compensate for the amount of bacteria you're going to remove. You might have to watch the levels for a week or two afterwards (the tank may go through a 'mini cycle').
It might be a messier job than you expect, CC can hold a lot of detritus. I'd probably remove as much water as possible, then remove the fish, corals and rock and put them in holding tubs with heat and circulation. When you remove the CC, the remaining water will probably end up full of detritus, I'd remove it and toss it. Then replace the rockwork, add the sand, fill the tank (consider the water used to replace the discarded bit a water change) and check the parameters. Once you're satisfied the temperature, pH etc. are fine, add the corals and fish and you're done.

Someone who has actually gone through the process of replacing CC may have a better idea. Minus removing CC, the above is what I did when switching from BB back to sand - I removed everything and threw out the last bit of water because it was full of detritus from disturbing the rockwork.

[MayoBoy]

I'm in the midst of doing it right now. There's no way I can remove everything so I'm suctioning out the sand with a piece of tubing. I suction out 5 gallons at a time and usually get about 1-1/2" of crushed coral before the bucket fills up with water. I've done it 4 times now and am about 1/3 of the way there.

I'm not worried about removing bacteria, etc because I have 100 lbs or rock or so, a sump and a fuge. I do let the bucket sit for 15 minutes or so to give the snails a chance to crawl up the sides so I can toss them back in the tank.

My biggest problem is finding the time to do it - I'm hoping to finish it this week sometime...