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rstruhs 
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 Topic: Plenum or not to plenum
Posted: May 12 2004 at 4:48pm |
I just bought a new/used tank and visited the GARF site to get some ideas on DIY projects. While there, I "discovered" what they call a "plenum" setup and suggest using it. I know this is not a new idea and it may even be old! Does anyone have any thoughts on whether it is a good idea or not? Here is a link:
http://www.garf.org/BulletProofReef/3rdbeginner.html
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Rodney, Sandra, Jeffery, and Laura Struhs
South Jordan, Utah 98th South & 40th West.
(801) 282-2744
75 gallon reef
55 gallon reef
55 gallon FOWLR
20 gallon FOWLR
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reptoreef
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Posted: May 12 2004 at 6:43pm |
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My sump/refugium is equiped with a plenum. As far as a neccessity, that's all up to you. There are a number of oppinions with the plenum method. As for me, I like the idea of the plenum method. Research in full the mechanics and idias of the plenum system as there are a few downsides... Restrictions of sand dwelling spp etc.
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jfinch
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Posted: May 12 2004 at 7:47pm |
The more I think/read about it the more I think a plenum is a waste of space (no offense intended to anyone using one). The idea behind the plenum is to allow a space for low nutrient water (actual plenum area) which acts as a "wick" to draw more nutrients into the sand bed and it's anerobic bacteria. The critters in the sand bed are not important... it's all about diffusion.
The theory behind deep sand beds (with or without plenums) is that the bugs in the sand move the water through the bed to the anerobic zones. Diffusion plays no role.
The truth might be somewhere inbetween. Maybe. But if it was all an issue of diffusion then a plenum should work in a freshwater tank too. And as far as I know they don't. I think the reason plenums work is because of the bugs and if that's the case then it's wasting space that could be sand. Just my current thoughts...
Or have I missed something about the plenum?
Edited by jfinch
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rstruhs
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Posted: May 12 2004 at 10:13pm |
Reptoreef and Jon are both successful aquarists, so there must be some value in having and not having a plenum!
I can appreciate the benefits of a plenum in a sump/refugium so I believe that to be a valid idea. I will probably try it in my new sump/refugium.
Jon brought up the wasted space issue and said it is all about diffusion. Jon also said that plenums do not work in fresh water aquariums. Good points too.
The plenum should provide greater exposure to the sand and its' accompanying anerobic bacteria. Then it would follow that a plenum would be beneficial.
Maybe, as Jon points out, the answer lies in the middle?
What would happen if we put more concentrated, oxygenated water through the plenum?
At what depth does the sand in a DSB become less helpful? 2", 6", somewhere in between or can we not achieve that point due to the size of our mini-reef?
Thanks for your help and opinions so far!
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Rodney, Sandra, Jeffery, and Laura Struhs
South Jordan, Utah 98th South & 40th West.
(801) 282-2744
75 gallon reef
55 gallon reef
55 gallon FOWLR
20 gallon FOWLR
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reptoreef
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Posted: May 12 2004 at 10:29pm |
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In Dr. Goeman's (revised 2nd edition) "Live Sand Secrets", there is, in fact some input and info reguarding successful freshwater and brackish plenum systems.
Edited by reptoreef
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jfinch
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Posted: May 12 2004 at 10:48pm |
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Really? I personally think if plenums worked (Natural Nitrate Reduction method) in freshwater tanks they would be all the rage. Do a search... all I could find was a few people discussing them for a planted tank (and using it as a way to inject nutrients for the plants) and a couple references to Goeman's booklet. I have a hard time taking Bob serious on any subject. Do you know of any freshwater systems using a plenum? I would love to incorporate one into a cichlid tank!
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reptoreef
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Posted: May 13 2004 at 12:19pm |
I have seen them implemented, but did not personally test. However, the particular display areas looked really spectacular. BTW, these tanks were Tanganican and Malawi cichlid systems. This was also about 3 years ago when I was doing maintanance while I owned and operated my own LFS.
Jason
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jfinch
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Posted: May 13 2004 at 12:43pm |
That interesting. When I get time, I'm going to tear down my son's freshwater tank and put a plenum in it.
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Jake Pehrson
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Posted: May 13 2004 at 2:55pm |
 jfinch wrote:
That interesting. When I get time, I'm going to tear down my son's freshwater tank and put a plenum in it.
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Jon,
Don't go to the dark side.
Deep sand beds work great in freshwater tanks also.
Edited by Jake Pehrson
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jfinch
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Posted: May 13 2004 at 3:33pm |
I've not had good luck with them. Well if you call 3" of fine sand a DSB. I always fought nitrates (20 - 100 ppm from water change to water change). My cichlid tanks looked a lot like a reef tank, lots of rockwork and about the same amount of sand (although I've only used silica). Doesn't a DSB in a reef aquarium require worms and other bugs to pump the water through it? I was under the impression that in a freshwater system the motive force in the mud was insect larva. Maybe it is diffusion???
What do you know/think about the idea that the denitrification in our tanks is occuring in/under biofilms?
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Mark Peterson
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Posted: May 13 2004 at 3:48pm |
Been there done that... I wouldn't waste any more time and space on a plenum for a marine aquarium. Sand beds on the bottom worked just as good as my plenums and I had several. The hype about plenums and the reason I tried it originally is discussed in an article in the June 2002 Sea Star Online.
It was really a good thing that Jaubert brought it all to our attention but the Monacco Aquarium also had a 10% direct ocean water exchange daily. So that makes useless, the conclusions about plenums based on the "father of the plenum".
Cindy Jones, long-time hobbyist and a Founding Member of the WMAS has kept Discus in her plenum operated fw tank for about 6 years. It works great and has tons of Anubius sp. plants. I know she would not change it. FW has much fewer bugs to do the work that we see in a marine aquarium DSB, so I wonder if there may actually be a slight advantage there. 
In the end, for a marine aquarium, both methods seem to work about equally well, so use whatever spins your bottle 
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