By Bob Goemans
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Real Reef Rock 

Bob Goemans corresponds with Todd Schwarz (Dalton, GA)

Todd Schwarz (Dalton, GA) writes...

Hi Bob,

I bet you thought I had fallen off the face of the earth! Well almost. I've recovered nicely from an illness that caused me to shutdown Reef Renovators a few years back. Making custom-made plenum grids was part of that business and I'm again interested in starting up a small business that will include making custom-made grids. In fact, just set up my cousin with a 20-gallon African Cichlid tank (with a plenum of course). It's doing great!

Recently Petland opened locally and decided to check it out. I spotted the 30th Anniversary issue of FAMA and thought I'd just take a peek. I started reading this great magazine in 1985 about the time the Smit wet/dry series came about. I was happy to see Julian's Reef Notes was still there, and low and behold so was Sand Mail! Wow I thought, wasn't everyone using either algae or mud refugia? So I started reading and was absolutely amazed to find someone asked you about a company making plenum grids! Must admit I felt a little emotional you had to tell them it was out of business. So decided to write and ask a few questions.

First: Is there still a market for plenum systems in general, not necessarily pre-made, but are people still using them with success?

Second: I looked over your 'great' website before sending this message and noticed Julian Sprung describes the use of Enkamat nylon matrix, such as I used on my past EcoSand Plenum grids. Is that product still available to hobbyists?

Third: Do you think a small part-time enterprise to specifically supply custom-made plenum grids with or without the Enkamat would fly? My thought here is a simple website business where one could place and pay for the order, such as with PayPal. The site would include pricing, shipping data, and photos of the material and finished products.

Fourth: Would I be able to advertise on your site and would you mention that custom-made plenum grids of different styles were now again available?

Warmest regards,

Todd Schwarz

Dalton, GA

Bob replies...

Hi Todd,

Long time! Odd how things go sometimes! And happy to see you're well again!

As for turning down people wanting custom-made plenum grids, have done that about 3 or 4 times over the past couple of years. I sent a couple of requests to your old email address, which did not go through. So that should answer your question as to demand, at least through my email. Nevertheless, the plenum is still somewhat popular, yet still misjudged as to its efficiency. And I've tried to convince people to use it in an interconnected aquarium/sump, as it's far easier to maintain if no rock or coral is on its bed surface. And I should add, many people are having greater success when done in this fashion, so the method is still popular, but there's still some resistance to it, - sad, but true!

As for the Enkamat, my thoughts are its better to have a sandbed where a dull knife blade can be run through the bed to discover clumps, which are caused by fast forming bacterium and calcium precipitation, and then crumbled with fingers. I also don't recommend the separating screen anymore in 99% of the setups because of this clumping issue. Keep in mind if the matrix blocks one's surveying capability, then bed efficiency will radically drop if the clumps cannot be broken up. As for the material itself, have no idea as to its availability.

Nevertheless, it would be nice to again have a source for custom-made grids, and would be happy to advertise that on my website at no charge and in my email when feasible. And suggest giving people the option of either a plain-Jane model or one with the matting on top, which honestly, I would not recommend in marine systems, but where African Cichlids are concerned that would be advisable!

Otherwise, nice to hear from you and am willing to help,


Todd Schwarz (Dalton, GA) writes...

Hi Bob,

Thanks for responding and I'm willing to admit that I'm disappointed the matrix idea has not worked out as well as I had hoped, but it was an interesting thought, and felt it should be explored.

Love the idea of putting the plenum in a sump. It solves a lot of the logistic problems such as having it covered with rock, using 6" of main tank depth, making sure it doesn't show from the sides, not being able to examine the bed fully, etc. Didn't realize clumping was as much of an issue as it seems. I'm very interested in being a source for whatever type plenum grids are desired.

Have some further questions; in your opinion what would be the simplest and most effective design? On that thought have a few ideas and questions about how people are using them in sumps. Are sumps usually lit these days such as a refugium, or have they become a separate unit apart from the sump? If they were lit, would there still need to be a small amount of space around the plenum grid sides to allow some sand down over its edge to block light? What has been found to be the best height of the open water space under the sandbed? And how big of a sump/sand bed are we talking about for a heavily stocked 55-gallon reef tank? A 20 or 30-gal tank? This would not be enough to supply much calcium to the tank would it? Or is calcium supplementation with something like 'Aragamilk' the way to go?

It was very nice to hear from you.


Bob replies...

Hi Todd,

When it comes to sumps, some are solely used for housing equipment and others used as refugia. In some cases, a little of both are combined. The problem as I see it, is with the goal of the system and its associated equipment not being too well planned out before the system is initiated. In my opinion, there's not a better form of 'biological' filtration then what's accomplished by the Jaubert plenum method! With that said, there's some resistance to its use because of past improper usage and/or poorly thought-out/worded articles describing the process.

Past experience with this method shows the plenum grid should be located in an interconnected tank/sump having a sandbed surface area that is about 20 - 50% that of what's in the main show tank. With that said, this 'sump' bed surface area should be as unencumbered as possible, as its this sand surface that is the area where diffusion takes place, ridding the bulk water of its nutrients. In some ways, this surface area is no different than that of an inexpensive mechanical filter pad - block its surface area and it removes far less matter. So simple logic dictates that if it were in the main tank with lots of live rock and corals upon its surface, it would perform less efficiently than if it was in an unencumbered interconnected tank!

Furthermore, an interconnected plenum system is far less expensive, far more efficient, and requires far less maintenance than do other forms of sumps/refugia that are set up for filtration purposes. With that said, and to be fair, other type refugia systems produce interesting looking environments rich in infauna and macroalgae, and if that's part of the system goal, so be it. Nevertheless, I prefer a nutrient poor method be attached to my aquaria, than a nutrient rich method. In fact, the plenum set up is usually so nutrient poor that it can't support alga growth therefore no lighting is needed. It should simply be considered 'the' biological filtration system, which reduces the amount of sand and live rock needed in the main show tank.

Don't take that as I'm against other forms of refugia filtration, but their goal is not the same as the interconnected plenum sump/tank. There needs to be a choice here: either it's a highly efficient biological filtration system or something that will be treated as an additional small aquarium with various animals and algae so as to present an interesting showpiece. And yes, opposite lighted nutrient rich refugia with macroalgae have some benefits, such as helping to stabilize the pH during nighttime hours. But would this additional 'aquarium' be needed if the system as a whole remained nutrient poor? That's a question not adequately faced/answered by some in the hobby. But, in my opinion, most systems are overstocked, overfed, and therefore require additional tools/cost and maintenance time to be kept adequately running, and a refugium is one of those additions. An interconnected plenum system is not, as its there as the 'heart' of the biological filtration processes!

As to the grid butting up against side panels, I never did like that as light would encourage alga growth near the bottom 'plenum' water filled space, as that is where some nutrients are temporarily stored until the bacteria on the sand above utilize them. (I've already explained that cycling process in the past, so if you missed it, contact me and I'll reiterate it.) In the distant past when the grid was being placed in the main show tank, this unsightly look along the tank sides was of some concern, yet simply running a 'chop stick' along the area between the side panel and the grid side cleared that up quite easy. But if the plenum is in an interconnected sump under the aquarium and enclosed in a cabinet, little or no algae would form along its sides even if the grid butted flush up against its side panels. Nevertheless, I would recommend the grid be about ¼ inch short of all sides of the aquarium.

I've probably made 200 - 300 grids of all sizes since 1991 when I made my first one! For large aquaria, I would make several sections, as most aquariums have limited access from above. Past experience has shown the best way to make them is as follows; for aquariums less than 100 gallons, I recommend ¼ inch high legs. For 100 to 1000 gallons, 1/2 inch legs. Over that, ¾ inch legs. As for the screening material, common fiberglass window screening is the best choice. The material should not only cover the top surface of the grid, but also its surrounding edges so as to prevent sand from slipping in around its outer edge. Place the top face down on the screening and then neatly fold enough screening up and over its sides, trim the excess and secure the bottom folds with some nylon thread. This makes for a nice neat looking grid having its top and sides enclosed. And if PVC tubing is used for the legs, drill some holes in them to allow for diffusion to the surrounding water.

As for calcium supplementation, even though the pH is somewhat reduced in the bed itself, it can not be counted upon to keep the bulk water calcium level where it should be, i.e., 380 - 430 ppm. Therefore, when it comes to reef tanks, I recommend a quality calcium reactor or various calcium supplements.

I should mention the success seen in freshwater aquariums with plenums over the past decade! An African Cichlid society and myself got together about four years ago to test plenum grids in a variety of their aquariums. I asked CaribSea to help with the experiments and they provided all the substrate free. It was an overwhelming success, with plenum tanks having far reduced nitrate levels than what did those with equal bioload without plenums! And even goldfish and plant tanks have had very good success! So your thought about the Enkamat product, especially where Cichlids are concerned, is a good idea!

Hope this helps and keep me posted.




Plenum; Auxilary Plenum

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