Substrate under live rock;good or bad?

[Marinemom]

O.K. Here's a question I've been wondering about. In a reef tank that has live rock and corals and one anenomne; if there is substrate underneath the live rock, is this going to cause a problem? I have gotten conflicting answers on this subject and I'm just not sure what the real answer is. The substrate in my reef is crushed coral that is about 1 inch thick. The substrate under the live rock is not as thick but it is still there. Is this a problem? Will it cause dead spots in the tank? What about anarobic spots? Do I have to worry about that? Obviously I can't move 77 pounds of live rock every time I do a water change. I have a clean up crew in the tank as well as a sandsifting snail to rummage through the substrate. I can't see how this is enough to keep the tank where it should be. These critters cannot get underneath the live rock very well. Do I have to move the rock structure to get what is under the rock? I do not want to remove the crushed coral from the tank because this I'm sure will lead to more problems. If I have to do this, can I just move the substrate foward so that it is in front of the live rock? Will the substrate be to thick and will this create an uneven balance in the tank? I'm sorry for all the questions but I figure that if I have to do this than I should do it now while there are no longer any fish in this reef. The one fish that was in there is in quaritine for a while just to make sure that he is O.K. before putting him back in the main display or adding any other fish. Of course they will have to go in quaritine first. Any advice and/or suggestions would be greatly appreciated.

Marinemom

 

[boxfishpooalot]

well you can say its bad and its not really. Denitrification(nitrate removal) requires an organic per se to complete its task. So as stuff builds up under the rock and the bacteria do their job better.
But, as stuff builds up and bacteria break it down to chemical elements it releases phosphates wich can cause algae to grow.

But, as solids build up under the rock you can build up toxic hydrogen sulphide. Wich is a gas that excapes easily but deadly. The problem occurs only when the sand is disrupted, releasing the gas.

Most people put rocks on the sand its not really an issue.

 

[reefnetworth]

advise! remove the CC. i know you dont want to but its better in the long run. your bacteria needs a place to live. live sand such as arag-alive is the best substrate IMHO. it also has millions of bacteria already living in it. over 20,000,000 per pound, along with calcium, carbonate, magnesium, strontium, molybdenium, potassium, etc. the bacteria eats nitrite, nitrate, ammonia. this is the bio-filter in nature along with live rock. this will house your snails and sand sifters much better and covers more surface area per square inch than CC. good luck and REEF-ON!!!

 

[Marinemom]

So what about this hydrogen sulfide that you say is toxic? If I start to remove crushed coral from the tank and the crushed coral from underneath the rock, is this going to release this gas? What about the corals and the anemone that are still in the tank? Will I need to remove them during this process or can they stay in the tank? My guess is that I will have to remove them. If so, what do I do with them? Most of the corals are softies with some stoney corals such as frogspawn, branching hammer, and a doughnut coral. They cost me quite a bit of money and right now they are fine and growing very well. I do not want them affected by this process. If I remove the crushed coral, will this throw the tank into a mini cycle? How will this effect the corals and the anenomne if I have a mini cycle? Or If I use Live sand, will that take care of this problem? Again, sorry for all the questions but I want the best possible conditions in this tank. I'm just not sure on how to get there.

If anyone can advise me on the best way to do this with as little upset as possible, please do. All suggestions are welcome.

Marinemom

 

[socalchris]

Marinemom: I was also a bit concerned about this, as I started with crushed coral and ended up putting about 3-4" of LS on top of my crushed coral. I am switching tanks because I never had a painted back, so when I switch I will probably try to get all the crushed coral out and use only LS, unless I hear otherwise.

 

[N8ster]

The other piece of advice I have seen several times is to place the rock directly on the bottom of the tank, and then add the sand. This will depend on what livestock you plan to put in your tank, but any tunneling under the rocks can cause the rocks to shift later, which can cause problems.

 

[bertoni]

The only sure disadvantage of putting live rock on top of the sand or crushed coral is that burrowing fish, etc, might cause a rockslide. The hydrogen sulfide issue doesn't seem to be much of a problem, in practice, although removing the substrate might be an exception. When I've removed substrate, I've broken down the tank completely.

There aren't very many clear answers to a lot of questions about our tanks.

 

[GreenBabe5]

I actually just switched my 20H to a 28Bow because I hated the CC and ordered LS from TBS and to avoid the hassel i bought a whole new tank and stand but to tell you the truth it looks similar because the sand is already seperating into larger broken shells and thin sand but all my sand sifters seems to be actually moving it and circulating it unlike the pure crushed coral which i hope will keep from creating toxic chemicals in it. I wish I had never bought CC but oh well i was in a rush, impulse buyer (hense the buying an entire set up just to change substrate)

 

[poppin_fresh]

My tank has a CC bottom and I hate it. I think a lot of my algea problems are due to the CC trapping stuff. I have began siphoning small areas of it out weekley so I can replace it. Once I get an area to bare glass I am going to add sand.

P.S. I also have my LR placed on top of the CC and have had no problems with it being there.

 

[DgenR8]

I'm not a fan of crushed coral substrate, but I wouldn't tell you that you have to remove it without at least asking what kind of readings you're getting for Ammonia, Nitrite and Nitrate.
You said:

Most of the corals are softies with some stoney corals such as frogspawn, branching hammer, and a doughnut coral. They cost me quite a bit of money and right now they are fine and growing very well.

If your tank is healthy, and you are happy with how it looks leave it be. If you are having water quality issues, or you're not really liking that CC anymore, removing the existing substrate is not difficult.
To get back to your original question, detritus will naturally accumulate in the substrate, and CC is notorious for traping waste. Dead spots under live rock are certainly no exception.

 

[Marinemom]

The readings on my tank are ammonia-0,nitrites-0,nitrates-0
P.H.-8.2,and S.G.-1.026-1.027. I guess in the long run I will be happier with the sand in my reef tank. The reason I used crushed coral instead of the live sand was because I was told that the sand would be a problem for HOB filter. The filter I'm using is an emperor 400. Now I do not see this as a problem now because I have a freshwater tank where I recently changed the substrate to a sand substrate and I have two HOB filters . So far there have been no problems with the sand and these filters. However the uplift tubes do not go as far down in the aquarium. I guess I'm just wondering about this poisonous gas that can be released into the aquarium if I move the crushed coral. If I move some of the crushed coral out a little at a time say a little each week over the course of several weeks will I still have this problem?If I leave the crushed coral that is under the rock, is this really a problem down the road?A little bit of the cc being removed at a time will not cause the tank to go into a mini cycle, right? How will all of this effect the corals and the anemone that are still in the tank? I wish I had used sand from the very beginning and did not listen to what everyone I talked to said at the time. Now I just want to fix this before this becomes a major problem?I really appreciate all of you taking the time and effort to help me. Any more advice or suggestions will be welcome and appreciated.

Marinemom

 

[DgenR8]

Removing the CC a little at a time would be the only way to go. As you remove the established CC, you are removing the bacteria on it. Doing it a little at a time allows your system a chance to catch up with itself. It is important that youy remove the CC close to your rock very carefully. it may be supporting your rock structure, and as you remove it, a rock slide could happen.
You really don't need HOB filtration if you have a decent amount of healthy live rock. HOBs won't hurt anything as long as you keep them clean, but really aren't necessary.
Live sand is also an excellent means of natural filtration. I'm not sure I believe in Live Sand in a Bag, but I know that a little live sand from 3 or 4 local reefers added to a dead sand bed will turn it live.

 

[bertoni]

I've taken CC out of a tank before. I did it by disassembing the tank, ditching the CC, and throwing in dead sand. Remvoing it a bit at a time is probably safer, though, and will work if your rock structure won't collapse along the way.