If you have crushed coral, and are going to keep it, then yes, you should be agressively cleaning it when you do waterchanges. You need to get as much gunk out of there as you can.
There are several options for a
DSB. You can certainly add one to your tank if you wish. This would be the most difficult, but by far the most helpful. it will be a real
PITA because you will have to remove as much of the crushed coral as you can before adding the sand. But, because the crushed coral is currently colonized by bacteria, like the bio-balls, you can't just take it all out at once, especially if you're removing the bio-balls as well.
I'd tackle one, then the other, not at the same time. Say you take a month to remove the bio-balls, then another month to remove the
CC. Once you have removed as much of the
CC as you can get, you can go ahead and add the
DSB to the display. because you will not be adding it to an existing sandbed, there shouldn't be a problem adding it all at once. It'll make a mess, and your water will be cloudy for a while, but it will be OK. For an effective
DSB, you'll need between 4"-6" of sand. The catch with a
DSb is, it takes a while to become active. On the order of several months. If adding one to the display tank is too much hassle, you can use what's called a remote
DSB, which is basicaly a 5 gallon bucket about 2/3 of the way full with sand, and only a couple hundred
GPH flowing across it. If that's the route you'd rather go, i can get Bobby over here to explain how he has set his up. Same deal though, it will take a while to start reducing
nitrates.
Feel free to hit us with any questions you have, or if anything is unclear. We're here to help as best we can
