Sand question

[kadiya]

Hey all I have a couple sand questions,
I have a 55 gallon and I want to have a dsb. I was thinking around 4" would be good. I heard sugar grain sand has like a half life of 18-24 months and that it needs to be added to or that a really DEEP dsb needs to be started up, so would 4" be ok? Or should I do like 5 or 6" instead?
Also I was told by one of my lfs that it would be good to put some rubble in on top if I want to get a sand sifter like a goby so that the sand doesn't keep collapsing on it when it tries to burrow. However, I heard the larger your substrate the more you have to worry about waste build up. Would a little rubble like crushed coral on top be ok, or would a goby be just fine with only sugar grain sand?
Ok last question, I read on garf that a plenum would be good to use with a dsb, however, I've read that a plenum doesn't really help unless you have a really large tank. Would it be more beneficial?

 

[moneyman]

Fine sand has 1/2 life of 24 months? That's crazy thinking... ... Might be because you suck them up during water change. I would go with 6" because there will be hills and valleys in your aquarium.
Rubble on top is a bad idea just of what you said. CC requires vacuming and you'll likely take out your sand.
I know you did not ask ... but, just FYI: Most people run their DSB in a fuge. This is because they dont want to look at 6" of sand. For your 55 gallon, the bottom 1/3 will be sand. The other 2/3 will be water.

 

[thomas712]

For a 55 gallon tank I would suggest no more than 80 pounds, this should give you about 2 inches or just over the bottom edge of the black moulding. The goby would not be causing any rocks to fall this way and still keep the sand clean, but most likely will not be able to tunnel either. But you can arrange your rock structures to help him out, by placing some rocks with cave like structures on the bottom that he can get into by digging into the sand.
If you try that and prefer more sand then you can always add more at a rate of 1/2 inch per week if you like. Perhaps even start out with only 3 inches and go from there.
IMO garf grunge sucks, its full of aiptaisa and is nothing more than junk that piles up in there aquariums. Its nothing but shells and rock droppings with some coralline on it.
A plenum is one nasty thing if you ever have to take it out. I don't hear to many people using them anymore.

 

[turningtim]

I agree with Money, A dsb in a 55 takes up a lot of valuable room in the tank. It also is not the most appealing thing to look at. I just removed a dsb from my 55 b/c of these reasons. Also if you run a refuge a dsb is kinda overkill b/c you have macros that will do the denitrification rather than need a dsb.
JMO
Tim