Substrate change out

I am going to change out my substrate, taking crushed coral/aragonite out and putting Caribsea Seaflor in. In another thread I described an on going fight against green slime/cyano. It is back and at this point I believe the substrate is loaded up and needs to be changed out. It is four years old in my tank, and I got it from someone else, who knows how long it was in theirs. I would prefer to swap it out all at once. Pull the rocks, fish and coral out, remove and retain as much of the water as I can, then remove all of the old substrate. New sand in, and everything back in the tank. I have enough tanks and heaters to maintain everything outside the tank while I clean, etc.

I have seen advice recommending changing out a portion of the old substrate at a time to avoid releasing too much debris into the tank. This is assuming the chaneg happens while the tank is occupied. With everything coming out of the tank until the clean sand/water goes in I don't think this will be a problem.

Any thoughts on partial changes versus doing it all at once?

I've done it a couple times but with shallow beds that had been vacuumed out ahead of time and during removal. Your way would be fine and probably easier/safer although I would take the opportunity to change out as much water as possible instead of reusing much.

if you want to re-use the water, be sure to remove it before disturbing the sandbed. If you contaminate it with the stuff in the sandbed, it can be disastrous to your corals and fish. Just remove the water into buckets, then whatever is left in the tank, consider it gone.

I have done this before, but not all at once. You may see a small cycle, but it shouldn't be too bad.

Yeah, that's what I did. I ended up siphoning out maybe 1/3 of the tank for reuse, which went into a 29 gallon temporary tank. Then rock got moved over and new water added to the 29. Once I started removing rock the water got pretty messy, so everything else went down the drain. Then coral, then fish. The project is done, everything went back into the original tank yesterday with new substrate. The tank looks much cleaner and everybody is much happier. It was a pain to do, but worth it.

On a side note, the morning that I had planned to move everything back the 29 sprung a leak overnight. Lucky it was in a fish (utility) room, so no damage, and I caught it before too much water had left, so no losses. Whew!

Seems like leaks are going around. Sue, seaponygirl had one this weekend too. Glad to hear you got the sand all prettied up. Good to know you're hanging in there with the hobby too, Paul.

Ok to do large water changes. I prefer them over several small changes. I try to do 30-50% per month. Keep us posted on your results. I applaud your endeavor. You might save the old strata and do a lengthy fresh water flush. A poreus (sp?) bag chucked in a lake or stream for a year or two. Save it to make some live rock of your own. Theoretically the nutrients should be able to flush out. But as cheap as it is, you could just fill a pot hole.