plenumn question

[sarmo]

i went to the GARF site and looked up how to make a plenumn. i can't find "nylon" mesh for the plenum space or for mid way in the sand bed. i found "fiberglass" mesh and i emailed GARF to see if it would work but so far no one has responded. has anyoune here used fiberglass screen door mesh for a plenum? do you think it is reef safe? the other question i have is how deep should the sand be? 4 inches 6 inches or what?

thanks for any help you can be.
rob

 

[Velamondry]

Not sure on the fiberglass mesh for the plenum, but for a DSB you need 3-6 inches depending on grain size, if its Oolitic (sugar sand) 3 inch's is fine. But the larger grain size you have the more sand you need, also keep in mind as time goes on your sand will decrease just from the Ph shift in your tank dissolving some of it. Incase you havent tried Wetwebmedia's website they got a ton of information on just about everything in an easy to read/search format.

 

[sarmo]

if you believe GARF, a plenum helps take care of nitrate. does a deep sand bed do the same?

 

[Velamondry]

Yes to an extent it all has to do with the way nitrates can be reversed in the chemical process from nitrates to nitrogen gas and sulpher dioxide ( if I remember correctly) What your looking for is a way to isolate an area of water where nitrates can be leached to it and oxygen does not reach. Basically a nitrate enriched environment and an oxygen deprived.

 

[tallguy64]

The real idea behind the phlem is this....

Take a sponge set it in the sink and pour water on to it. the water splashs off and not really through it.

now hold that same sponge up and pour water on it. the water will flow through it rather then over it.

Thats the same principle your going for with a phlem, you can have the water flow through the sand rather then just passing over it. i have read good and bad things... i am doing a modified version in my tank. so far seems to be working well... im useing a silica sand with no division between uper and lower sand.. because it is smaller grain size and wolnt disolve over time i am able to use a 4" to achieve the same effect as a deeper sand bed and so far its working good. but the real questions with phlem is how long it will last before it causes problems.

 

[sarmo]

seems like that is a problem with DSB's also. the "solution" i've read is to keep the sand depth above 4", assuming fine sand.

PS- fiberglass mesh is fine based on "The New Marine Aquarium" by Paletta. i had the answer on my book shelf.

 

[fireftrjn]

I HAVE HEARD that plenums are outdated technology.????
???? Are refugiums are now the way to go.

 

[sarmo]

that brings up another question. does it matter if i have macro algea growing in the sand of the plenum?

 

[freetareef]

no it doesn't matter but if you have tangs they will eat your macro.

I made the plenum from the garf website and i am a big fan. water DOES NOT flow through the plenum. it is there to create a o2 devoid space to house bactiera that complete the nitriogen cycle. I also used the fiberglass mesh and it worked fine.

the recipe from garf calls for a specific sand for thier depth, i would listen to it. I have talked to leroy @ garf many times and if you want to get ahold of him and ask a million questions call him by phone he will anwser during buisness hours.

The main drawbacks you hear about in pleniums and dsb's is the hydrigen sulfate pockets that end up getting disturbed and crash your tank. The REMEDY for this is to introduce microfuana that stir the sand bed. slowly. and for ever. hence GARF GRUNGE, this is the key ingredent that add the hundreds of small brittle stars and shrimp and everything else for a deverse living sand bed. "Live sand" as is sold at the lfs is a shell of real live sand beds.
In calfos new book he states the use of both dsb's and pleniums with not much difference between the two.
If you do the plenium my suggestion to you is to do the 2 inch of sand, the screen, then three inches of sand on top. I say this because if you are seeking a high flow envioment such as a sps tank, the top layer will get moved a little and i pointed a power head at the glass and when i woke up the sand was blown away down to the screen and potentually oxigenate your o2 devoid space. which from what i understood wouldn't crash your tank but your tank might go through another cycle as the o2 depleated bacteria begins to replenish. that was a worst case senario.
I lmao when i read posts like "my poisionus sea apple died and released poision in the tank but i think the plenuim crashed my tank..."
I believe the rate of disaloution in to the plenium is about 15 or 20 days...
just my .02!

 

[freetareef]

more sand is ok I would not use less for special seaflor grade sand.

 

[sarmo]

thanks for the info about the GARF Grunge, do you still think i need it? this plenum is in a 150 gallon stock tank that will have macro algae only, no livestock. i am planning on removing my current sump (40 gallons) and having the overflows from my display drain into the "fuge" with the plenum. then from there the water will gravity feed to another stock tank that will act as my new sump. and a new return pump will bring the water back to my display. my display is about 5 years old. i was planning on siphoning my displays sand to get a "live" culture into the plenum. i was also going to move some of the live rock to the plenum. do you still think i need the grunge? and do you think i need the pipe and powerhead to "suck" flow into the sandbed?

thanks

 

[MikeS]

In order for a plenum to be effective, you need to have decent water diffusion in and out of it. Many people make the mistake of having too fine of sand on top of them, you are better off with a more coarse grade of substrate.

Here's some reading...

http://www.saltcorner.com/1024/index1024.htm

Go to the "guest articles" section, there are several good articles on plenums and sandbeds....

 

[sarmo]

thanks for the link. good reading i got the sand that GARF recommended. sepcial grade reef sand.

 

[freetareef]

thats the sand i got also. if you read the garf site they have water flow through the plenuim till it is done cycling but thats it. for the remander of its life (some are over 10 years and still going strong) they are o2 devoid and have no flow.

also i get awsome ca readings from my sand bed with no supps. last night was 500 with dkh @12 so alls good there.

 

[freetareef]

i didn't do the flow through at all. it may speed up the process but i didn't do it and it is fine.
about the grunge i would say yes, especially since your talking about stock tanks. their iis so much micro fuana that i'm sure the corals would love to eat if they floated by.

 

[freetareef]

hey fire i think it depends on your bio load. i am doing both as one or the other probly couldn't keep up alone. but i have 12 fish during the cycle so what do i know...

 

[sarmo]

i think i'll pass on using the pump to suck water through the sand into the plenum. i think you make a good point about the plenum being remote from the tank so i'll get some grunge to get it a proper seeding.
anything else i should think about?