DSB Heresy

[Clay Glover]

Apologies if this question is redundant, this is a lengthy thread.

How long have you been implementing the CPW, and have you noticed any detectable increase in NO3 levels. Do you feed on the lighter side, or do you feed enough to keep fish overweight?

Good answers....

 

[Mojoreef]

LOL ldrhawke I guess when you tank is only the size of one of the sump compartments you think in different terms
I gues what I am trying to say is that your system may get rid of some of the long term build up waste, but I can see it dealing with P at all, plus it still has a blend of several different forms of nitrogen mixed through out it. I dont think you will be able to break bacterial bonds on the sand particles which is also binding most of the organics.
Your system although well thought out would likly make the anaerobic zone take hits on its every draining...no??? which would lead to an even less effective ammount of denitrification.
why not skip the decomposing phase??? thats what a dont understand.

Your discription of my system is pretty accurate but a tad out of context. the water flow is designed to recreate an enviroment for the critter i keep. Most reefs have a tad of flow the sump is really just a sump, the mangrove dont really do much either, but a gift all the same. on the controller, with alot of equipment you tend to need one.


MIke

 

[ldrhawke]

I guesS what I am trying to say is that your system may get rid of some of the long term build up waste, but I can see it dealing with P at all

YOU MAY WELL BE RIGHT, BUT SINCE THE PHOSPHATE DOES ACCUMULATE IN THE BED AND SINCE THE BED pH IS LOWER THAN THE WATER COLUMN. IT MAY AT LEAST HELP TO REDUCE THE AMOUNT OF PHOSPHATE IN THE WATER COLUMN. ONLY TIME WILL TELL. I DO BELIEVE SOME SORT OF PHOSPHATE FILTER WILL STILL BE NEEDED IF YOU HAVE A HEAVY BIOLOAD, BUT MAYBE SMALLER THAT IT WOULD OTHERWISE NEED TO BE SIZED FOR.

, plus it still has a blend of several different forms of nitrogen mixed through out it. I don't think you will be able to break bacterial bonds on the sand particles which is also binding most of the organics.

IT MAY NOT REMOVE WHAT IS BOUND, BUT IT WILL REDUCE THAT WHICH REMAINS OR GOES BACK INTO SOLUTION AND IS CONCENTRATING IN THE BED. AT LEAST IT IS NOT ALLOWED TO BUILD UP TO THE POINT OF CRITICAL MASS AND TOTAL DEATH.

Your system although well thought out would likely make the anaerobic zone take hits on its every draining...no???

THAT DEPENDS ON THE WASTING RATE TO SOME DEGREE. I CONTEND THE OXIC AND ANOXIC ZONES ARE NOT UNIFORM LAYERS, BUT HAVE PEAKS AND VALLEYS AND HIGH AND LOW VELOCITY ZONES. JUST LOOK AT THE VARIATION IN COLOR AND APPARENT ACTIVITY IN THE BED THAT IS EXPOSED ON THE BOTTOM OF THE TANK THAT YOU CAN SEE THROUGH THE GLASS (ACRYLIC)

I CONTEND THIS ASSURE YOU ALWAYS HAVE SOME DEGREE OF DENITRIFICATION TAKING PLACE. AND IT NOT YOU HAVE NITRIFICATION TAKING PLACE THAT REPLACED IT. WITH CPW YOU TRY TO MAINTAIN A FLOW INTO THE BED REMOVING THE NITRATES AND OTHER WASTE.


which would lead to an even less effective ammount of denitrification.

REMAINS TO BE SEEN. EVERYONE SEEMS TO BE CONCERNED THAT USING CPW WITH REDUCE DENITRIFICATION AND MOVE THE NITRIFICATION ZONE DEEPER INTO THE BED. EVEN IF IT DOES REDUCE THE DENITRICATION RATES, IT IS ALSO REMOVING AND STOPPING THE HYDROGEN SULPHIDE BUILD UP. IT IS ALSO INTEREFERRING WITH DENITRIFICATION. I CONSIDER THIS A MUCH GREATER POSITIVE.


why not skip the decomposing phase??? thats what a dont understand.

IF YOU WASTE ENOUGH A CPW TO A LARGE DEGREE YOU ARE DOING JUST THAT. THE HISTORY OF BB AND SHALLOW BEDS IS THAT THEY CAUSE NITRATE BUILD UP IN THE WATER COLUMN. OF COURSE YOU COULD ALWAYS INSTALL AN ELABORATE SYSTEM INTO TO COMPENSATE FOR THAT TO REMOVE THE SOLID WASTE LIKE YOU HAVE DONE.

CPW IS NOT MEANT TO BE A TOTAL SOLUTION. IT SHOULD BE CONSIDERED ONE MORE DEVICE AND TOOL TO GIVE YOU MORE CONTROL ON WHAT SHOULD NOT BE HAPPENING IN YOUR TANK.

 

[ldrhawke]

Apologies if this question is redundant, this is a lengthy thread.

How long have you been implementing the CPW, and have you noticed any detectable increase in NO3 levels. Do you feed on the lighter side, or do you feed enough to keep fish overweight?

Good answers....

I installed the system when set it up in May. It has only been running with CPW for about three months.

I have seen some slight variation in NO3. It is always just barely detectable on the test. I contribute that to the heavy bioload and feeding.

My fish are fat and sassy. Although I have started watching how much and what I feed more closely now.

 

[ldrhawke]

TiTAN wrote on 01/30/2004 05:23 AM:
Hi,

Just wondering, I have been reading your thread on CPW and it sounds very interesting.

I am thinking this could be just like a Coil Denitrator in priciple as if the flow out the Coil-Denitrator is to slow it produces Hydrogen Sulphide(Could be wrong) with is exactly what you do not want so increase the flow. Well from what I understand that is exactly what you are doing with a CPW method? Removing Nitrates?

So from removing the water from the plenum at a certain rate you would still achieve the same result as in a coil Denitrator? Or not? Except you are not returning the water to the tank/sump?

I have been thinking about implementing your CPW method for a long time now and I think I will do it.

What would you change in your CPW setup to make it better or more efficient?

Thanks for your time.

Gunter
___________________________

There are some similarities. The idea is not to have hydrogen sulphide in either case. In the case of a coil you are producing it if you do not keep a high enough flow and it interferes with denitrification, but with CPW you want to remove what is produced in the bed.

You are right that if you only removed enough fluid with CPW that only hydrogen sulphide was eliminated regularly, you would keep the hydrogen sulphide from interfereing with the denitriifcation and have better denitrification in the bed.

If you only ran CPW to accomplish that and removed very small amounts of fluid daily, it would make for a better DSB system. That is another way to run CPW. Which anyone using it could opt to do.

Would I make any changes to make it more efficient? No. It gives a uniform controllable drain across the bottom of the bed and I can back flush it to maintain it if it should every start to blind. That's all I designed it to do.

This is a good question Gunter. Do you mind if I post it to the list?

______________________________


Hi,

It is not a problem at all, I was going to do it but I was not sure so you may do so whenever you like.

So now if you made the a system that used a CPW method and made the DSB +-5" instaed of +-4" and made a drip rate or flow rate high enough to make sure you did not get Hydrogen Sulphide you would infact have all the benifits of the DSB(Critters) its Denitrification Potential and have alot less of its bad side and plus you would not be wasting so much water as you would be feeding it back into the system as it would not have Hydrogen Sulphide in it.

I am wondering from your experience would that work and maybe even making the DSB +-6" so the flow could be set at a higher flow to get the nitrification and not have the Hydrogen Sulphid so it could be passed back into the system just like using a Coil Denitrator.

Thanks for your time

Gunter

____________________________

I considered doing that at the start and it is another option. I didn't because of four things 1)the coil would need to be very large to get adequate turn over and flow rates to be affective. (I don't have the space) 2) going though the expense and having another support system with a coil seemed to be a waste of money and effort. 3) I needed to make water changes anyway, it seemed foolish to go to all the effort to recycle a little water and then dump even more into the drain. 4) regular fresh salt mix elimates need for a lot of expense trace element additives


_______________________________

So if you added an extra inch of sand to you DSB and increased the flow of your CPW that would thoeretically elimiate the bad side of DSB period, becasue you can highten the screen in the middle and keep the top 2 inches turned over by the critters so this would be a good way to go don't you think?

Thanks again for your time

Gunter
-------------------------------------

Go for it.......:rollface:

 

[Mojoreef]

ldrhawke you dont really have to set up an elaborate system or some huge amount of flow to remove detritus. It just has to be properly designed. I have alot because my tank is sixteen feet long. the filters are just thier for a once and awhile running or when needed.
Anyway I am not trying to put your system down, as far as it looks it is probibly better then a standard fall off the log dsb. its just the whole concept of holding onto waste/food/detritus that does not make sence to me.

Mike

 

[ldrhawke]

ldrhawke you dont really have to set up an elaborate system or some huge amount of flow to remove detritus. It just has to be properly designed. I have alot because my tank is sixteen feet long. the filters are just thier for a once and awhile running or when needed.
Anyway I am not trying to put your system down, as far as it looks it is probibly better then a standard fall off the log dsb. its just the whole concept of holding onto waste/food/detritus that does not make sence to me.

Mike

First, I never thought you were trying to put CPW down. Second, I don't think there is any significant difference in our approaches after looking at your web page. The only real difference I see is that you have a shallow bed and I have a DSB. In fact, I use the same Dolphin 3000 pump on my 60 g system that you use on your 1000 g system, and I also direct the flow around the tank using changing out lets.

The problem is even with my high energy input to capacity ratio, all of the fish poop is still not kept in suspension and most settles to the bottom. It quickly breaks up and my bed surface is always clean, but it does not get picked up and put into my bag filter. Unless you've potty trained you fish, I don't imagine your tank is much different.

Also, I believe a considerable amount of the fish and coral waste is liquid excretion.

Based upon the fact that all the waste is not easily physically removed, you only have two choices left...biological or chemical treatment. If biological treatment is done properly it is the cheapest and most stabile method.

With this in mind, I believe the more biological surface area you have in a tank, the better. Thus I am trying to improve upon the DSB and make it work better.

I believe the second most important item after biological treatment is the skimmer. Then chemical absorption with carbon and phosphate absorbing media to further improve the water quality.

A well designed biological system can take a lot of the load off of the skimmer and filters.

So you see, for the most part we are really in agreement:mixed:

 

[Mojoreef]

yep the thin layer of CC was an experiment that only lasted a few months, I found it was just trapping detritus like all substraight do. so I pulled in a few month back and went back to the original BB again. I find that I can get the vast majority of the detritus out, a quick blow of the rocks usually gets the balnce back in the water column.
Your system is very close to a sytem that charlie has been using for a number of years, te only different is that his is a plenum (or was your a plenum to??). But it does all the things your system is striving for. I think the big difference is however is the particle size. thier is done with larger particles following the jeaubert system a little closer.

good luck on it and I wish you the best of luck.

Mike

 

[DougSupreme]

are there any concerns with using CPVC as the piping in this system? Not sure if it saltwater safe, and I would rather be sure before I bury it in the sand

 

[ldrhawke]

are there any concerns with using CPVC as the piping in this system? Not sure if it saltwater safe, and I would rather be sure before I bury it in the sand

CPVC is fine.....it can even take high temperature and stand up if you boil the water in your tank.

Infact, now that i think about it for a minute, it is a great idea. CPVC is better than PVC because you can get CPVC in a smaller size than the smallest 1/2"PVC comes in. This would allow you to build a plenum with more pipes for an even more even distribution of flow. i wish I would have used it.

 

[salty joe]

Really interesting thread. It makes perfect sense to me to export pollution from where it is concentrated.

My problem is, I like the look of fine sand mixed with CC & rubble. I am thinking of lining the bottom with PVC drilled with 1/4 holes & maybe bigger farther from the siphon. Set eggcrate lined with 4 or 5 layers window screen. Any sand that sneaks past screen will get flushed out with waste water. It seems to me that this should create a fairly uniform "pull" on the bottom of the sand bed.

Even if channeling occured, I'm sure it will, I wonder how much nasty stuff would migrate from sand into plenum in a day from osmosis. Hopefully enough to make a difference.

The thing that has me bugged is a couple years ago, I set up a plenum according to Goeman. After 6 months, it solidified. It was replaced with a DSB accordind to Shimek, with no problems. Never ever used additives- always used a Ca reactor. I can't say for a fact the plenum caused solidification, but it is my gut feeling. And Goeman does mention using a butterknife or something to bust up hardened substrate.

 

[cuongvynguyen]

ldrhawke, thanks for the great writeup and answers. If I had seen this thread a year ago I would have set up CPW also as it looks to be a no risk, benefit situation which makes it a no brainer for me if I had to do it again.

Some members here were looking to have sand inhabitants in their tanks. My tank is far from looking as nice as any of the tanks here, but hopefully someone else will learn from my mistakes.

I have a 180Gal tank, of which my total volume of water is roughly 170 gallons. 250lbs of live rock, DSB, protein skimming, and occasional activated carbon and phosphate obsorber serves as filtration.

The tank has been setup with the DSB (0.5mm grain) for over a year and I have enjoyed keeping 4 queen conchs which are getting quite large (4+ inches and growing) as well as a pair of twin-spot gobies which do quite a job of stirring up the sand bed, and occasionally digging deep into them looking for meal. Other inhabits include 4 small clowns, 2 medium tangs, 1 watchman goby, as well as a red scooter blenny. My non fish inhabitants includes an assortment of soft mushrooms, 2 5' clams and a single acropora which can be seen here: http://reefcentral.com/gallery/showgallery.php?ppuser=19355&cat=500&thumb=1

Before the DSB the tank was setup with CC (which was a nitrate sink) for 3 years before tearing it down.

As seen in the photos I have lately been having to deal with high phosphates levels due to overfeeding. I try to keep some diatoms growing to keep the conchs happy and simply overdid it due to my own neglect and not maintaining the DSB at least bi-weekly if not weekly.

 

[ldrhawke]

Really interesting thread. It makes perfect sense to me to export pollution from where it is concentrated.

My problem is, I like the look of fine sand mixed with CC & rubble. I am thinking of lining the bottom with PVC drilled with 1/4 holes & maybe bigger farther from the siphon. Set egg crate lined with 4 or 5 layers window screen. Any sand that sneaks past screen will get flushed out with waste water. It seems to me that this should create a fairly uniform "pull" on the bottom of the sand bed.

Even if channeling occurred, I'm sure it will, I wonder how much nasty stuff would migrate from sand into plenum in a day from osmosis. Hopefully enough to make a difference........

Joe,

The concept of a a plenum fewer small holes and being directly covered with filter cloth, reduces the normal short circuiting of flow through the substrate. The idea is to obtain a more uniform flow through the substrate and not have it all come through a shallow area with lower resistance and not move through an area that is partially built up with waste or more dense material. This will keep more of the substrate fed with the waste from the water column above.

As I have tried to explain, bigger holes and and egg crate covering them, allows for the fluid in the column to find the shortest and easiest path into the plenum. This will encourage short circuiting.

When you build a plenum your way, you will end up with a complete open space under the substrate, and the water column above will always find the path of least resistance to enter it. All of the flow into the plenum can then come from one small area.

A couple of you 1/4" holes could probably accommodate the total flow being discharged from the system.

Picture the flow in reverse to better understand what I am trying to do to get a more uniform draw through the substrate...........as a test hook a garden water hose, from your home, up to a 10 foot pipe drilled with a bunch of 1/4" holes. Each 1/4" hole can flow over a couple gpm each at only a couple of psig pressure.

Turn on the water.....you will see nearly all of the water flow will come out of the holes in the first couple of feet of pipe closest to the hose connection.

Take the same pipe and make the holes smaller, only 1/32 or 1/16" dia. Run the same test. You will now see water being discharged more uniformly form one end of the pipe to the other. Too many holes or too large of holes and you have the same maldistribution problem all over.

The same phenomenon is happening in a plenum in reverse.

 

[Shoestring Reefer]

The concept of a a plenum fewer small holes and being directly covered with filter cloth, reduces the normal short circuiting of flow through the substrate. The idea is to obtain a more uniform flow through the substrate and not have it all come through a shallow area with lower resistance and not move through an area that is partially built up with waste or more dense material. This will keep more of the substrate fed with the waste from the water column above.

What happens when the filter cloth gets clogged? If the bed is not loaded uniformly with waste, some areas of the filter will be clogged sooner than others, and short circuting will occure.

When you build a plenum your way, you will end up with a complete open space under the substrate, and the water column above will always find the path of least resistance to enter it. All of the flow into the plenum can then come from one small area.

Picture the flow in reverse to better understand what I am trying to do to get a more uniform draw through the substrate...........as a test hook a garden water hose, from your home, up to a 10 foot pipe drilled with a bunch of 1/4" holes. Each 1/4" hole can flow over a couple gpm each at only a couple of psig pressure.

Turn on the water.....you will see nearly all of the water flow will come out of the holes in the first couple of feet of pipe closest to the hose connection.

Take the same pipe and make the holes smaller, only 1/32 or 1/16" dia. Run the same test. You will now see water being discharged more uniformly form one end of the pipe to the other. Too many holes or too large of holes and you have the same maldistribution problem all over.

The same phenomenon is happening in a plenum in reverse.

I believe the maldistribution would only occure if the hydraulic resistance of the bed is low, ie, if the bed is shallow and a large substrait like crushed coral was used. With a deeper bed or a bed with finer material, what will realistically happen is this: water will flow uniformly through the bed, and only the flow in the plenum will be maldisributed. This is because the pipe maldistribution will be insignificant compared to the resistance of the bed.

First, picture it this way:
Drill TWO pipes with holes; one with 1/4" holes, and one with 1/32" holes. Place them side by side, and pipe water to them. True enough, the pipe with 1/4" holes will have undistrubited flow, and the pipe with 1/32" holes will have a more uniform flow out of each pipe. The problem with this analogy is that a plenum system or a buried pipe system is more than just the pipe or the plenum; the effects of the bed on flow distribution must also be considered.

Now Picture This
Drill a 1" pipe with 1/4" holes, and drill a 3" pipe with 1/32" holes. Place the small pipe with big holes inside the big pipe with little holes, such that water must flow through the 1/4" holes, then the 1/32" holes. Turn the water on, and the flow distribution out of the little holes will be no worse than the single pipe with little holes. Placing the pipe with big holes inside will not cause a flow maldistribution through the pipe with little holes.

How this relates to an actual set-up
In the pipe-in-pipe example above, the 1" pipe with 1/4" holes represents the piping in the plenum, and the 3" pipe with 1/32" holes represents the bed. Flow within the plenum may be non-uniform, but flow distribution through the sand bed will be affected by the sand bed, not the plenum piping.

 

[Flanders]

Did you take any precautions (screens, etc.) to make sure the jawfish don't short-circuit your plenum? Most of this discussion is over my head, but I wondered about the jawfish.

 

[ldrhawke]

Did you take any precautions (screens, etc.) to make sure the jawfish don't short-circuit your plenum? Most of this discussion is over my head, but I wondered about the jawfish.

The whole purpose of thr plenum design I recommend is to eliminate that concern and problem. The Jawfish digging a hole is a good example.

Even if the Jawfish dig down and expose part of the plenum, you still get a draw down through the rest of the bed because the exposed area has a highly restricted flow from the exposed zone because of the small orifices. If you had large orifices in the plenum, all of the flow would be pulled throgh the Jawfish hole. Very similar principle we use in our industrial processing system for even air distribution into waste.

 

[Dr-BYTES]

what is the material your drainage cloth made of any possibility of it rotting after years in saltwater.I am setting up a cpw system on my new 65 gal and i want to make sure i get everything right

 

[ldrhawke]

what is the material your drainage cloth made of any possibility of it rotting after years in saltwater.I am setting up a cpw system on my new 65 gal and I want to make sure I get everything right

You can buy polyester felt type material used as a soil drainage barrier at Home Depot in the garden dept. Any of the synthetic felts and screens will be ok for saltwater. Wrap the piping like you would a package with a couple of layers. Use coarse crushed coral if it is a DSB.

Make sure it is piped so that you can reverse the flow to backwash it. Two ball valves and a Tee should be all you need connected to the drain line. This will allow you to hook up an external pump and feed backwards into the CPW system. Reversing the flow for 10 or 15 seconds is all that would be required when you do back flush it.

The drainage flow rates are low and blinding should not be a problem. My system flow is still fine and has not needed to be backwashed since I installed it, but it may eventually. It is a good idea to plan ahead.

 

[Dr-BYTES]

CPW

CPW

thanks for the info one more question do i use crush corel for the whole bed or crushed corel on the bottom and sand on top
also the 1/32 holes would it benefit then being on the side of the pipe or on top

 

[ldrhawke]

Re: CPW

Re: CPW

thanks for the info one more question do i use crush corel for the whole bed or crushed corel on the bottom and sand on top
also the 1/32 holes would it benefit then being on the side of the pipe or on top

Personally I would use all Carib Special grade crushed coral. That is not to say it will not work with a shallower sand bed. I just think the crushed coral will have less of a tendency to blind.

Point of Interest. Recently I have read a number of reports describing simultaneous nitrification/denitrification taking place in municipal wastewater treatment plants. In large racetrack carousel systems that use aerators to pump and aerate, forcing the water around the race track in an oval. Inbetween the aeration/pumping stations the oxygen is used up so rapidly, my the aerobic microbes, that denitrification takes place in the quiet zones. An aerobic waste treatment system will go anaerobic with 15 to 20 minutes, if oxygen is not continuously supplied.

When testing the CPW plenum I found the discharge was not only anoxic, but it would start producing H2S if it wasn't regularly wasted.

Drill the holes on the side of the pipe. I used additional lengths of pipe and set them in loose to partially fill the gap between the the CPW plenum piping. I did this to keep the felt cover from totally collapsing around the pipe from the weight of the sand.