Why are UGFs frowned upon for marine tanks?

blasterman_

blasterman_

AC Members
Jan 6, 2008
94
0
0
50
(UGF = Under Gravel Filters)

.....But Wet/Drys and gimmicks like Bio-Wheels aren't? I don't get double-standard even though all three function on the exact same principle. If anything, because a UGF is *in the tank* it's far less likely to fail due to power outtages and mechanical problems and less likely to cause a crash.

I should note that I wouldn't be caught dead using any of the above in a marine tank, but if you put a loaded gun, er, skimmer to my head I'd pick a UGF.

Extra credit:

My most stable marine tanks have always been my tanks with DSB (deep sand beds). What potentially would be the effect of combining a DSB with a very slow turnover UGF plate in terms of nitrate fixation?
 
Part of the problem with a UGF is that most of the filter plates have holes that would allow sand to sift through them. Also, isn't the principle behind a DSB the creation of an anaerobic zone for denitrification? If you were pushing water through the DSB, it seems to me that it would completely negate those benefits.

Also, coming from a FW perspective, wet/drys and biowheels don't function on the same principle as a UGF/RFUG. An undergravel filter is using the gravel as biomedia. The advantage to w/d and biowheels is that the bacteria colonies are constantly exposed to air, making them more efficient. The fundamental idea is the same, i.e. providing surface area for beneficial bacteria growth, but the efficiency of a w/d is not the same as the low flow principle applied in a UG filter.
 
blasterman_ said:
(UGF = Under Gravel Filters)
My most stable marine tanks have always been my tanks with DSB (deep sand beds). What potentially would be the effect of combining a DSB with a very slow turnover UGF plate in terms of nitrate fixation?
Click to expand...

DSB helps with nitrate because of the anaerobic spots that exist houses special bacteria that consumes nitrate.

When You have an UGF, the point is to provide oxygen to your substrate to house nitrification bacteria, which is aerobic, therefore, defeats the purpose of having a DSB.
 
^ unless you go RUGF with a sufficiently deep sand bed. Best way I've seen to do this is to make your UGF from drilled PVC (holes parallel w/ tank bottom) wrapped in plastic screen. Add a layer of coarse dolomite or rubble (keeps sand out of the RUGF plane), then a nice DSB on top of that. Despite *some* water circulation through the DSB, there are plenty of spots where diffusion rules and N2 can be produced. If I ever do a FOWLR or reef, it will likely have this sort of setup. If it causes trouble, I'll just pull 3/4 of the sand and make sure I have some active sand stirrers in addition to the goby/shrimp pair that would likely be among my first inhabitants.
 
Also, isn't the principle behind a DSB the creation of an anaerobic zone for denitrification?
Click to expand...

I'm trying to create something more efficient and practical than a nitrate coil while improving the efficiency of a DSB. I'm also talking about a very slow water turnover through the UGF/DSB - like a couple GPH and not sticking a 800 GPH power head on it.
The fundamental idea is the same, i.e. providing surface area for beneficial bacteria growth, but the efficiency of a w/d is not the same as the low flow principle applied in a UG filter.
Click to expand...

Why? Because markting people at Pengiun say so? Nitrosomas and nitrobacter grow anywhere there's oxygen, low light, something to cling to, moist and reasonable warm. Dirt in your back yard is full of them. Why then is a plastic, rotating wheel or bucket of plastic balls *out-side* the tank and prone to the whims of power failures better than a UGF which is in the tank and constantly immersed in tank water? Actually, if I think about it, I see little conceptual difference between a UGF and LR/Berlin method other than the UGF (with strong current flow) being less prone to nitrate fixation that does occur to some extent in large pieces of LR.

Despite *some* water circulation through the DSB, there are plenty of spots where diffusion rules and N2 can be produced
Click to expand...

Exactly what I was getting at my friend! For me, nitrate reduction is a far, FAR more critical concern for reefers or general marine tank owners than Ammonia/Nitrite fixation which will occur anywhere on anything.
 
Undergravel has been used in salt tanks for years successfully.

I run a partial under my 4+ inches of sand. I have 1/3 of the bottom (end) with the undergravel

My understanding of how the sand works is that it actually creates its own movement of nitrogen with pressure and the actual migration of the gas.

An old cast iron boiler heater system as and example I guess is the closest to it. Those heat exchangers only have one pipe going to them yet they get hot.

So in theory when you put the undergravel filter in the deep sand bed, the negative pressure disrupts the natural exchange of the nitrogen and other gasses created in the sand bed.

The french drain style mentioned above sounds like a great system.

The deep sand be is good for SW plants. The substrate will decompose nutrients for the roots of the plants to use.

I'm sure there is alot more going on in the biological sense, but that is my basic understanding of it.
 
Thanks guys. While I may seem a little blunt, I'm merely trying to get people to think outside the box.
 
Last edited by a moderator:
Grins said:
Hmm not sure whom you are talking to but I don't know anyone that recommends wet/dry filters or biowheels for a marine tank. Most I respect actually recommend to stay clear of them as well as UGFs.
Click to expand...

Oh I know of several LPS that do.. In fact back in the day I was one of the people who was told that this was an acceptable practice. But I think the research has advanced to a point where there is still a lot of misconceptions out there simply because people don't update websites.
 
You must log in or register to reply here.
AquariaCentral.com
Top Bottom