Quick dumb question, how much LR and Sand is required

[hotwire73]

I forgot the ration of LR pounds per gallon, and sand formulas. If you know please refresh my memory. In your fomulas state if its for LR only, sand only, or both. TY

[IslandCrow]

A generic rule of thumb for rock is 1 to 1.5 lbs per gallon. For sand, there really isn't a rule, especially since you don't even need sand if you have sufficient live rock. If you're looking for how much sand you need for your sand bed to have a certain depth, I believe there's a calculator linked somewhere on the homepage. As far as sand depths, I'd recommend 1-2" for a shallow sand bed, and 4-6" if you plan on doing a deep sand bed.

[der_wille_zur_macht]

Can you give us the dimensions of the tank and your desired sandbed thickness? There's a calculator linked from the RC homepage that'll tell you pounds of substrate to achieve a certain thickness given that information.

For live rock, it's really up to your preference, as long as you're in a reasonable range. Most people quote rules of thumb in the 1 - 1.5 pounds per gallon range, but I see many issues with that approach. Firstly, it doesn't take into account the differences in density, size, shape, porosity, etc. among different pieces of live rock. Secondly, there's no real solid scientific justification for needing a certain amount, so even if you could nail all the above variables, you'd still have no solid basis for suggesting a certain amount. There are plenty of examples of successful tanks with everything from half a pound per gallon up to two pounds per gallon, so there isn't even any informal backing to a given rule of thumb.

So, put live rock in the tank until you're happy with the look. Some people like a ton of rock - they'll probably end up near 1.5 lbs per gallon. Others like an open structure - they'll probably end up well under 1 lb per gallon.

[hotwire73]

K 72" long, 25 Thick, 30 Tall; around a 235 gallon tank. Also anyone got that link for the calculator (i.e. the one that you put diminsions in to get tank gallon volume)?
Der_wille, I was wondering how that would work when I have some rock that substainally more porous than others. But figured there was just a general rule of thumb. Ive been at 245 LR for awhile, but added 25-30 more today.
As for the sand bed I was thinking it had to be a minimal 4"s deep to be an active bio bed. I lost my old computer system and all my archive info. pertaining to these things.

[Trolldoll]

http://www.reefcentral.com/index.php?s=

Its on the Home page.

[hotwire73]

K troll found that, am I right about 4"s minimum to make an active bio bed?

[IslandCrow]

For live rock, it's really up to your preference, as long as you're in a reasonable range. Most people quote rules of thumb in the 1 - 1.5 pounds per gallon range, but I see many issues with that approach. Firstly, it doesn't take into account the differences in density, size, shape, porosity, etc. among different pieces of live rock. Secondly, there's no real solid scientific justification for needing a certain amount, so even if you could nail all the above variables, you'd still have no solid basis for suggesting a certain amount. There are plenty of examples of successful tanks with everything from half a pound per gallon up to two pounds per gallon, so there isn't even any informal backing to a given rule of thumb.

A very good point. My last tank (a 46g) certainly didn't have 46 pounds of rock. But then again, I only had two fish, so there's yet another flaw in the ROT. It should truly be based on your bioload and not your tank size. If you have no experience to go off of, though, it's not a bad place to start.

K troll found that, am I right about 4"s minimum to make an active bio bed?

This is not really true. 4" of fine sand is pretty much the minimum for what we commonly call a deep sand bed. The benefit of this type of sand bed is that the lower layer will generally have an oxygen deprived location where nitrate can be converted to nitrogen gas. This process is also accomplished by your live rock, so a deep sand bed is generally not necessary. Also, any depth sand bed can be an active biofilter. There are also potential risks with deep sand beds. Many of these risks do not necessarily have firm scientific backing, but you'll probably want to do some research in that area if you decide to go this route.

[hotwire73]

Thanks Islandcrow, I plan on keeping all my live rock, and actually adding 50+ pounds on next mondays order. I was just trying to find out how deep a bed needed to be to actually work correctly. Seems we agree 4" is minimum. Your stating theres other problems with deep sand beds, is it advisable to just stay around 3"s for my rock slides lol? Hard to keep a constant deep bed in my tank in one area, my triggers and puffers like to dig.

[IslandCrow]

Yeah, I had a maroon clownfish, so I had 0 sand around her area and 4-5" on the sides of the tank. I'm more of a fan of shallow sandbeds, though (1-2"). First, I tend to see deep sandbeds as a waste of valuable real estate and somewhat unattractive. . .or at least kind of strange looking. . .unless you do what I've seen some people do and build a stand where the bottom of the tank is actually recessed into the stand, so the deep sand bed looks shallow when viewed from the outside. Also, as I stated before, I don't think very many well-maintained tanks really need the extra de-nitrification a deep sand bed provides. And even if you do, a remote deep sand bed (one located in the sump or area other than the display tank) is often a better idea. Finally, you have potential issues if you have fish who like to push the sand around. One of two things is probably going to happen. If they're doing it constantly, you're not going to get the benefits of a deep sand bed, because that area is going to be well oxygenated from the constant stirring of the sand. Worst case scenario, deep sand beds can accumulate a good amount of decaying material in the lower layers that can release nitrates and phosphates into the waterstream if stirred up. Really worse case scenario, if the lower layers of your deep sand bad are too oxygen starved, they can actually accumulate hydrogen sulphide, which you certainly don't want getting released into your tank.

Anyway, I don't want to completely scare you away from DSBs. I have used them, and they can be beneficial, but there are also limits and risks in their use.

[luv my garden]

Hotwire? How did it go? How deep did the sand end up? Did 50# of additional rock cause any problems?

I'm getting ready to move my tank to another room and pondering these same things.