Undergravel filters

[slipgate]

Why aren't undergravel filters liked for SW tanks? I would think of all tanks, SW would benefit most from the water constantly circulating through the sand bed.

From what I have read, they are fine for anything accept some places say not to use on reef tanks with coral. Again, no reason why stated. I'd like to know the technical reasons since my experience and understanding of undergravel filters would suggest they are beneficial for all tanks.

 

[Khemul]

They often don't play well with sand.

That and generally anything that can trap debris and cause trouble with water parameters (canisters, HOB filters, UG filters) if not kept constantly clean is looked down upon in the SW world.


In a sense, the concept is used in SW. It is just in the form of closed-loops rather then undergravel filter plates.

 

[excuzzzeme]

The argument against their use in saltwater is the same one used in fresh. Not as efficient at mechanical, no real biological filtration, etc.etc. The sand will compact under it, no good flow... and the argument goes on. IMO - I don't see the wisdom of using them with a sand substrate, nor would I condemn the use when using a different substrate. Having seen them used in saltwater never surprised me any more than seeing them in freshwater would.

There has been quite a controversy raging for years about using them. You will find anti-UGF and on the other extreme those that say they are a must. It all boils down to what works the best for you. I used UGF's for many years (freshwater) before there were power filters, without problems. There are people today that still swear by them as well as those that swear at them. It call comes down to how well you maintain your system and your personal desires.

 

[the wizard]

I wouldn't use one in FW either. any detritus that gets down under there is there to cause problems. Not worth the risk IMO.

 

[dbosman]

Filters and filtering theories and filtering fads come and go. Stick around a few decades and see whats popular.
Some concepts still work really well such - as box filters, in appropriate situations.
Sponge filters work really well in appropriate situations. Particularly where the growth of micro-organisms is desired, such as fry tanks.
HOB filters work really well in a lot of situations.
Canister filters work really well in a lot of situations.
Under gravel filters still work well to really well in certain situations.

Some people used to run UG filters, maintenance free for two to three years, then the tank would go toxic. Doh! (or is it Duh! ?)
Some people think that since an Eheim or other large canister can go multiple months between cleanings that all canisters can. Not so.
Some people run HOBs until the impeller stops turning, and curse all HOBs.

One current use for UG filter plates is in shrimp tanks. Babies don't get sucked in, the whole gravel bed is a mechanical and biological filter.
But, they work best with the intake of an HOB or canister filters in the uplift tube to suck out all the mulm that would normally collect under the plate.

Some salt water folks are going back to the idea of an UG filter, only this time around it's called a plenum.
Your mileage may and probably will vary.

 

[LiveMermaid07]

very interesting.

the only thing I can add is I saw a diy ug filter and they put some sort of mesh screen over the filter plate to keep the sand out. (supposedly, don't know how well that works)

Does that make a differnce?