To Plenum or not to Plenum

dx7fd2 · 05-27-2004, 06:24 PM

I am going to start this tank with a plenum. I have read a lot of conflicting views on this subject from the DSB concept to the no substrate concept. The plenum is a concept I am familiar with. Any negative or positive experiences I should be aware of.

Thanks 3Reef population! [smiley=uhoh.gif]

JohnO · 05-27-2004, 06:42 PM

The DSB is really just an extension of the Plenum concept. IMHO both are flawed and I would use neither. All you really need is about 1 to 2 inches of substrate.

Any deeper than this and you are not creating the "nutrient export system" as is claimed by some 'experts' but rather a nutrient gathering system which will in a few years fail and probably kill everything in your tank.

John

btw. DSB = Deep Sh*t Bed :-)

jline · 05-28-2004, 01:46 AM

I used to have a plenum with about 2" of crushed coral in my tank. I found it difficult to keep clean, and had mixed results. I moved it to my sump by creating a devided area. It is easy to clean, about every 6 months, and my nitrates are zero. I purchased a new ro/di unit and a tds meter and my tank has never looked better.

Matt Rogers · 05-29-2004, 08:05 AM

Well this topic used to be a hot one... glad nobody has gotten to0 riled up. *

I have had a small plenum going the last few years in my plant tank of all things. Mine has layer of coarse and fine sand over it. It's a small tank and is really stable. Can't say anything bad except that it's probably not ideal for plant roots, but then again, they seem to grow right through it.

My current salt tank just has 3-4 inches of sand in it and it seems fine.

I think Rob Tooner (sp?) did a study on plenums and dsbs and didn't find much difference for what it's worth.

I kinda dig them for some reason though. Guess it's the DIY in me.

I would recommend if you do it though, you do what Bob Goemans does and make a remote plenum in a sump and not in the main tank. He feels it works better without rocks on the sand and it is easier to maintain with the access to it. I am pretty sure he uses a gravel siphon on some of it occasionally.

dx7fd2 · 05-29-2004, 11:15 AM

I am leaning towards the sump concept. I am starting from the beginning and have plenty of time to make decisions. Money is a fairly big consideration. Does a 20gal sump seem large enough for an 80gal reef tank? Obviously this will up the ante on the skimmer, but I was trying to convince myself to go with a Remora Aqua-C anyway. The difference between that and the Remora pro isn't that much. I assume I'll need a heater in the sump and the tank. Just in case of disaster I do own a Vortex Diatom filter that can easily be brought in to service. Excuse me, I digress, I read the article by Rob and he says that it is very easy to occasionally siphon some of the debris from the sump gravel.

dx7fd2 · 05-29-2004, 11:17 AM

Love those DIY guys!!!

Matt Rogers · 05-30-2004, 09:08 AM

I would probably go with something bigger than a 20, maybe a 30 long.

If you do it, I recommend wrapping the plastic window screening around the entire egg-crate foundation and folding it over and sealing the folds with silicone. Think of it like wrapping a Christmas present. This will keep sand out of the void better. Be sure to use the proper sized sand which is coarser than southdown. More like 2-4mm in diameter.

People used to do a coarse layer, then put more screening on it and fine sand over that. I personally think it's fine to do just one type of sand over the plenum about 4 inches deep.

Cool thing about doing it in the sump is it doesn't take away room in the tank and it's easier to maintain.

The benefits of a plenum are open to debate, but since I have one with sand (not CC), I can honestly say they don't hurt. Like I say in the sand section of this site, it's just one piece of the puzzle. If you slack elsewhere, this won't help you.