Controlled Plenum Wasting

[Matt Rogers]

I agree..

[quote author=inwall75 link=board=Sand;num=1087396461;start=0#8 date=06/20/04 at 14:33:47]
We are not replicating the ocean. *An ocean has hurricanes, upwellings, tides, etc. *We are doing our best though. *When dealing with closed systems, always remember..what goes into your tank..typically stays in your tank.[/quote]

Real good point inwall - well said!

[Craig Manoukian]

That ocean thing. Yup, see my signature!

[inwall75]

CAVEAT....I still have not read the whole thread on RC.

However, I do understand the basics of the thread. It's important to remember that sandbeds are primarily bacteria houses. They are the major workers and not worms.

(I apologize in advance for the vast oversimplification). Bacteria can break down organics into the raw materials....Phosphates, Ammonium, Sulphides, mulm (which cannot be broken down any further), etc. This system works well until the accumulation of nutrients, bacterial floc, and mulm overload the system. Once that happens, the sandbed will actually put Phosphates (from dying bacteria) and mulm into the water column. Since the sandbed can no longer process it down, to the left, right, front nor back, it goes the only place it can.....up into the water column.

IMO this system is designed to take advantage of the sandbed advantages and prevent some sandbed disadvantages. Sandbeds are great at processing but fill up over time...this system sacrifices denitrification for a short period of time but MIGHT make and sand bed last for a long time by providing a down and out option instead of only an up into the water column option.

There's nothing wrong with being open-minded.

[Craig Manoukian]

Are the phosphates and mulm released into the water column removed by skimming?

[cannon2222]

This is the first time that I can fully understand what a dsb does, thanks Craig! Sometime to understand something, the idea does need to be over simplified (at least for me!). I never realized how much crud there is until I looked. YUCK!!! I will be setting up a cpw in the new tank.



phil

[inwall75]

[quote author=Craig_Manoukian link=board=Sand;num=1087396461;start=0#13 date=06/20/04 at 18:33:06]Are the phosphates and mulm released into the water column removed by skimming?[/quote]

Any hydrophylic compound (as almost all nasties are), can be removed through skimming. Phosphates come in many forms and not all of them are hydrophyllic. In other words...yes and no.

Unfortunately for reef keepers, the world of organic phosphorus compounds is far more complex than inorganic phosphates. Many common biochemicals contain phosphate esters. Every living cell contains some. Molecules such as DNA, ATP, phospholipids (lecithin), and many proteins contain phosphate groups. In these molecules, the basic phosphate structure is covalently attached to the remainder of the organic molecule through one or more phosphate ester bonds to a carbon atom.

These bonds are stable for some period of time in water, but will eventually break down to release inorganic orthophosphate from the organic part of the molecule, a process that can be sped up through the action of enzymes in a reef tank. Many of these organic phosphate compounds will be readily removed from a tank by skimming. Export of organic phosphates is the major way that skimming can result in reduced inorganic orthophosphate levels in a tank. Orthophosphate ions themselves are not significantly removed via skimmate (since they do not adsorb onto an air/water interface), but organic phosphates can be removed before they are converted into inorganic orthophosphate.

An important point about organic phosphates is that they will mostly not be impacted by phosphate-binding materials sold to the aquarium hobby. Consequently, while these products may do a fine job of reducing inorganic orthophosphate, they may not help an algae problem that is caused primarily by organic phosphates.

A final point is that organic phosphates will not be detected by most test kits. Those that do detect organic phosphates (e.g., Hach PO-24) break the phosphate off of the organic compound and thereby convert it into inorganic orthophosphate prior to testing. However, these kits are tedious and expensive, and not for every hobbyist.

Here's a good link where the preceding paragraph came from. http://advancedaquarist.com/issues/sept2002/chem.htm

Mulm can be removed if it is blown into suspension and gets sucked into the skimmer. It is best removed via mechanical filtration or periodic water changes after turkey basting the rocks.

[Matt Rogers]

Cool good to know.. didn't know my mulm.

For the record, I asked Bob Goemans about this CPW stuff, here is his response (he said I could post this):

As for the drain plug, that's a ridiculous misconception started by someone
who tested the plenum area and found a higher than the bulk water nitrate
level and thought it would continue to accumulate and panicked! They simply
did not understand the inherit ability of the plenum method (how it
recycles those nutrients because of the difference in the negative charges
located the lower bed and the plenum area. The plenum is a reservoir, that
acts like a temporary collection area for those nutrients. Think about it *
there is often insufficient bacteria in the depths of the bed to handle
excesses, and in deep beds directly on the aquarium bottom, that's tough
dog poop and they simply accumulate and sometimes diffuse upward into the
bulk water. Not true in a plenum system, where those excesses are
temporarily collected in the plenum space and then cycled back to the
bacteria above!
Bob

Bob knows his plenums, I can't discount this, but I still like the idea of a drain - (especially on my turtle tank! What a mess!)

Well, nothing like a sand debate to keep the wheels turning!

[Craig Manoukian]

No debate if you are informed and plan accordingly. Maintaining your sand bed and water column is vital to the success of yor tank. It's all about controlling nutrient import and export.

[inwall75]

I'm not going to get into a public debate over this. I will tell you that Jaubert's system in Monaco is no longer a plenum because it was found that over time ammonium kept recycling in the plenum and the Ammonia levels were off the charts. Since Ammonia inhibits the first enzyme in denitrification, it was no longer even processing Nitrogenous compounds----hence, the high nitrates he mentioned. Jaubert's system is now an open system using purified seawater. If you don't believe me, do a Google on Jaubert Plenum and try to find a RECENT article about the Monaco Aquarium. This post may seem negative but it isn't. For the most part, I'm agreeing with Bob (I got to meet him at last years IMAC and he was the nicest guy). He recommends larger particle sizes so that maintenance can be performed on the bed on top of the plenum. IMO, this guy on RC is doing the same thing....draining out from the bottom as well as maintaining the top layer.

Basically, Plenums typically last longer than DSB's because of their advantages. However, they require maintenance too.

For those who want to go to the library, here's some interesting reading material.
Jaubert J., 1989. An integrated nitrifying-denitrifying biological system capable of purifying seawater in a closed circuit aquarium. Bull. Inst. Océanogr. Monaco. 5: 101-106

[dx7fd2]

I, like Phil, am going to go ahead and try a CPW.
Like I said in an earlier post I don't see how it could hurt, and if it does postpone the inevitable sandbed crash, than more power to me for trying it.
I don't know, but if in that amount of time, there will be a way to predict when it is time for a sandbed rebuild by analysing the crud that is coming out in the drained fluids.
I trust people like "GOEMANS" to a point, but after all, he has been involved at the core of Plenum/DSB debates for many years. I do recognize stubborness when I see it!!

Thanks for all of your input 3Reef!!

[glow=red,2,300]Let's keep the debate going forward!! [/glow]