Cpw - Why should you go plenum

B

BrianC

Membership Expired
[I avoid this issue like the plague. But, I am dieing for something intresting.

Contrary to what you may assume in reading my posts I am not against DSB, Bare bottoms, or plenums. However, I am very pro- CPW and I think it's the best system for nitrate reduction of all!

A plenum is the best system for Nitrate reduction. I can't explain how it works but, if set up correctly it could substantially reduce your water changes and still keep nitrates very low.

All I have to do is read this thread:

http://www.dfwmas.org....;t=7861

to know the concept should be fairly popular!

If you read http://www.dfwmas.org....;t=7861

you know that nitrates aren't as bad as everyone suggests for corals!

Lastly read this thread from January 17th at 11:55 read DR Shimek and Randy Holmes Farly quotes.

http://www.dfwmas.org....2;st=30

Then you know the plenum and DSB can have anoxic regions. If we have a petroleum engineer he/she can tell you how toxic hydrogen sulfide gas is!

Look if your name is not Dr Ron you probably aren't upto par on all the ins and outs of the DSB... contrary to popular belief it's not a beginner's concept. It's not just put 4" of sand in and everythings going to work out... there is alot more to it.

Same with this ideal; A plenum is a set of PVC pipe wrapped in window screen covered in crushed coral and sand.

A CPW is different in that the pipes are linked and glued together holes drilled and connected to a drain.

Myself and Scott Comstock have discussed it in depth and believe that you need to drain I would say 10% of the tanks combined water from the plenum. This should remove the anoix region completly.

It should be done either every water change or every other water change so once ever 3 to 6 months.

Depending on your tanks bioload you can stretch water changes for upto 3 months!]



Edited By BrianC on 1106624840
 
[This article by Eric Borneman is enlightening. His suggestions are easy to understand and to follow, and listed in the bottom 1/3 of the page.

http://www.reefkeeping.com/issues/2004-11/eb/feature/index.htm

Why is there a need to stretch out the water changes? Do you try special waxes on your car so you don't have to wash it as often? Special soaps so you don't have to bathe daily? Water changes are about the cheapest solution to most any need, and really aren't that big a deal once a nice method has been employed.]
 
[Did you notice Eric mentioned me in his article? He says, "there are a slew of people who probably should never have bought the tank in the first place." :)]
 
[I've had my tank since august. I have a DSB in the refugium and have macroalgae in there. Since that time I have done no intentional water changes. I did replace about 10 gallons a few months ago because my Ca was high. Initially my nitrates were up to 20 ppm. Since the DSB has matured (about 2 months ago, the bottom 3" are completely black now due to the anoxic layer) and the macroalgae has started growing my nitrates are not measureable and my phosphates are at around 0.075. I think the phosphates are greater than 0 because my RO filter doesn't have a DI cartridge on it (its on the way). My bioload is not low. It is a 25 gallon tank with a 15 gallon fuge and I have a purple tang, a yellow tang (who's scared of the tang police, not me!! :D ) two percula clowns and a green chromis. I feed the fish once a day and 1/2 a sheet of nori for the tangs (they are only 5" long). I feed the corals phyto and feed the tank rotifers once a week. I have a shallow sand bed in the tank because I eventually want a mandarine dottyback.

I say all this because I can only speak from personal experience. The DSB works for me. I have it in the fuge so that if I ever want to clean it out and replace it with new sand it is easy. From my understanding the plenum and the DSB both rely on the anoxic layer. I would think that the sand provides more surface area for the anoxic bacterial to populate. Correct me if I am mistaken.

I think you (Brian) are saying that the plenum is easier to maintain. If you are worried about hydrogen sulfide gas, doesn't the plenum create H2S as well? I though this was the result of the anaerobic respiration process where the product is H2S instead of H2O.

I am not advocating no water changes. In fact I may try one shortly (once my DI filter comes in). It is possible that there could be other toxins in the water, nitrate and phosphate not being a complete measure. I will see how the corals respond. Also new water may replace some items in the salt mix that I have used up or skimmed away. I have been reluctant to do a water change until now because I believe that since I didn't have a DI cartridge and am measuring about 7 (what is the scale for this) on my TDS meter at the output of my RO I am adding something (presumably phosphates) and I wanted to keep it down as much as possible (plus I am lazy by nature :blush: ).

Anyway, that my experience. I would like to hear thoughts on how the plenum is chemically different from a DSB. If someone could point out a link. I would appreciate.

Thanks]



Edited By Soji John on 1106670344
 
[Well, with two 5" fish in the 25g, you might consider sending them to a larger tank and getting a couple of 1" tangs again. ;)]
 
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Edited By BrianC on 1106712073
 
[Ron,

If you were talking to me and I think you were, could you let me know what you mean? I'm not saying that I'm not sitting on a time bomb. I am new to the hobby and would really like some advice. What warning signs should I look out for?

Thanks in advance,

-soji]
 
[Ron, The misinformation on DSB is astounding. I'm not saying none of them crash but look at this thread!

DSB Poll

They are not ticking time bombs. Even in this thread has only ~10% crashes and that is probably skewed up from the topic title. 10% could easily be explained by bad husbandry!

I'll leave it at that because I have no inclination to get into this arguement. Suffice it to say that every conference I attend I bring this up with the experts and none have told me a DSB is a bad idea!

I also agree with Marc in that just because your plenum does dentrify well is no reason to avoid or prolong water changes. If that was the case I would never do a water change as I haven't had detectable nitrates in a year in my big tank! Water changes are more important for other things such as trace mineral replacement (honestly we have no idea what corals really need so best to provide them as close to NSW as possible), metal/other nutrient export, etc.

Again not saying water changes are proven to be neccessary as there are successful tanks out there that have gone months or even years but in my opinionit is a very good way to keep your water stable and avoid many, many issues.

Brian don't take this as bashing your CPW. I find it to be a very interesting idea and time will tell if it works well or not. The upkeep is prety high since it calls for at least weekly (some people say daily) small changes. I also have some concern that when you extract the water from the bottom you will introduce to much oxegen to the "low oxygen" area and I think this could cause problems. Just my thoughts.]



Edited By kwl1763 on 1106717708
 
[Soji, fair enough.

You are adding nutrients to your tank daily with feedings. From what you are saying they are accumulating in the sand bed. One day through a gas release or saturation or a disturbance in the sand bed there will be a massive release of nutrients in the tank. Especially with a small tank this release can be fast and catastrophic. I'll bet your upper levels of the sand bed are already being cemented together like a rock.

I guess I am at the other end of the spectrum. My thin sand bed is only for appearances. I have all kinds of sand snails and sand sifting stars. So nothing lives in my sand bed. That's an over exaggeration but I try to keep a sterile tank with low nutrients.

Fish eat the food but most of the nutrients past back into the tank. then eaten by the clean up critters in the tank. then algae, macro and bacteria. The nutrients that aren't removed by respiration or bio mass (things growing) are removed by skimming and WATER CHANGES.

I have seen a lot of different successful and diverse systems, but all of them remove nutrients, in one way or the other, from the system. Thats is the whole idea of a plenum as I understand it

I hope I am not dishing you. just my opinion.

Good luck]



Edited By salsini on 1106720989
 
[Keith, I am not anti-DSB that is not the point of this thread. If your read the CPW you will find it entertains plenum and DSB ideals.

It's luducris that Dr Ron suggest there is no chance of Hydrogen sulfide gas build up in a DSB. The DSB has a 10 times greater chance of forming an unpermiable region than a plenum does.

If you look at how a plenum is built 1st 2 inches are sand that definetly aerobic, next 2 inches are crushed coral it's difficult for thiat layer to not be aerobic/anerobic... yet somehow and this happens often it becomes unpermiable. Making an anoxic region - no oxygen amd toxic gases build up Dr Ron actually suggest (in a DSB) that is healthy??? Any Dr or Vet will tell you a toxic gas being released in a controlled/ confined environment is deadly.

The CPW allows you to removed the build up in that region with a drain system. It's just that simple!]



Edited By BrianC on 1106750997
 
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