A few weeks ago I was having a problem with my tank that we could not really pin point the problem.  and started thinking it was a new salt mix.  In the last 3 week I have done close to a 100% water change and the corals are looking much better in general.  There are still a few Zoa's that are not happy and I have lost a couple of other smaller coral frags.  I could not say for sure that they were not sick before I did the water changes and switched over to my old salt again.  

Shelby,

If you are removing all of your current sand and replacing it with new then yes you can drain it and do it all at one time. You will still see a little stress from the reseeding of the sand bed but if you keep the rock in water so that you don't create a bunch of die off on it the re-seed cycle should be managable.

For what it's worth here is what I did when moving a tank with a DSB across the room. No losses, no cycle and the corals all looked great in 2 days after the move.

1. Drain 1/4 of the water into a tub for the loose corals. Then move the unattached corals into the tub. Run a small power head in the tub for circulation.

2. Drain the rest of the water to within 2" above the sand and place in tubs for the live rock and remaining corals. Get them into the tub as fast as possible and again add a power head for circulation.

3. Move the rest of The sand and water into 5 gallon buckets.

4. Clean out the tank and add about 6" of fresh tank water back into the tank.

5. I wanted to get all the rubble, old snail shells and junk out of the sand so I got a large colander with holes large enough from my sand to pass through then sifted all the sand and removed the unwanted rubble to some old tank water. You can use it for rubble in a refugium if you want. Keeping it wet keeps it live. I found it easier to fill a 5 gallon bucket with fresh saltwater and then add the sand to the colander and swish the sand around. The wet sand falls to the bottom of the bucket and the rubble remains in the colander.

6. Move as much sifted sand as desired back into the tank. The water will be murky but that's OK good nutrients for the tank.

7. Allow most of the sediment to settle and then re-position the rock into the tank. Add water to keep the rock submerged but not so much that it overflows when you add the rock.

8. Top up the tank and fire up the filtration. Use filter socks to filter out the fine particles.

9 Replace the loose corals and you're done.

The rotten egg smell you are smelling is hydrogen sulfide gas from anaerobic areas of your Tank. Washing the sand like this keeps the good bacteria alive and gets rid of the Hydrogen sulfide gas.

Good Luck.

Edited by bfessler - July 03 2013 at 11:07am

bfessler wrote: Oh try to use as much of the old tank water as you can. Just discard the dirty water used to sift the sand.

builderofdreams wrote: This is just my opinion and I mean no disrespect , but I thinking you are making a mistake by shocking this tank again. There is no way this tank has had enough time to start stalbizing its self from the last issue. There is other ways to address the Ph.   , which to me can be associated with the. recent death of your livestock and a percentage of death of your live rock and of course what ever was living in the sand Here is my thoughts. Open all doors to sump and open canopy. Fan wouldn't hurt blowing across sump. Remove the cup on the Skimmer And let your Skimmer oxygenated the water. Add another powerrhead and make sure the surface of the water is being violently agatated. Also keep changing water. I am just try to save Ya the work its going to take to do what your about to do. I can't imagine having to change my "sugar sand " in my 210 in the next 6 months.

If you've ruled out other issues and especially if there is a rotten egg smell in the tank I would stand behind you in reducing the depth of the sand bed. Depending on the severity of the problem I might reduce it gradually but if you're afraid of releasing high quantities of Hydrogen Sulfide gas because of the rotten egg smell I would probably go with your original plan.

Hydrogen sulfide gas is produced in highly anaerobic areas with little or no circulation. It's highly toxic and if left unchecked can cause serious issues with your tsnk. 2.5" of a coarser sand shouldn't be a problem but fine sand only requires about half as much to produce enough anaerobic area for nitrate reduction. Allowing 6" piles of sand to sit in your tank is asking for trouble.

Get some serious advice about the filtration in your tank from other members who have large tanks that are doing well and try to replicate it in your tank. DSB's in my opinion are better left in the sump/refugium than the display tank where you can maintain them without messing with your display. While I used to be a proponent of the DSB over the years I've changed my mind on their effectiveness and long term use.

Have you verified the PH readings are correct?

Well I got the tank drained and all the sand sucked out last night. It was crazy the 2 kinds of sand separated in to 2 layers. The very fine sand was mostly all at the bottom. It was so dense that wit a scraper it would come up in sheets? I did take a few pictures of it and what the tank looks like now.   I guess that there is a problem with the site I will try to upload the picture later

Yeah I added about 120 pounds of Aragonite Reef Sand to replace the super fine sand that I pulled out.  I was looking as some of the fine sand that was dried out and it almost looks like pure white playground sand.   I ordered Nature's Ocean Marine White Sand from Petco.  This is what 90% of the sand in the tank was made of.