Under sand filter

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Under sand filter

Post by adampetherick » Fri Sep 15, 2006 4:25 pm

Was thinking about under sand filtering for a tank and that the holes are going to be too big and suck up sand, also read somewhere that plants grow better in gravel so have come up with this


should hopefully suck the nitrates/nitrates over the plant roots which I believe I read that plants can absorb???

Was thinking the membrane between the sand and gravel could be made out of the stuff mosquito screens are made of with holes cut to put plant roots through and stop fish getting at them.

Any thoughts from people with more experiance in this area?

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Martin Thoene
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Post by Martin Thoene » Fri Sep 15, 2006 5:43 pm

Likely effect will be the sand compacting and reducing the water flow to a negligable rate where any biological filtration benefit will be minimal IMO.

Never tried it, but basically under-gravel filters are called that for a good reason, and I wouldn't recommend them for loaches anyway.

Image Resistance is futile. You will be assimilated.


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Post by adampetherick » Fri Sep 15, 2006 5:47 pm

What about the thoughts that plant roots grow better in gravel than sand and protecting the plant roots? So same as above without filtering, just gravel, membrane, sand?

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Post by shari2 » Fri Sep 15, 2006 5:55 pm

Personally, I've had great results growning plants in sand. Huge long root systems, runners like mad. They seem to root faster, if anything, than in gravel. Gravel does allow more of the fish poop to get to the roots, and I do use a fert bullet under the larger plants, but other than that, I've seen no diminishing of plant growth when changing from gravel to sand. I also provided fertilizer for larger plants in my gravel tanks as well, so I don't think that makes the difference.

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Sand versus Gravel, Bio-Filter approach

Post by wasserscheu » Sun Sep 17, 2006 4:32 am

I switched once from gravel to sand. Sand is having better results. I did that due to advice in a german forum. I use "seed-size" 1mm (0.04"), works great ,Here the link for pic´s


here some pic´s of work from Olaf Deters regarding "why sand"...


Regarding filtration, Olav Deters, is explaning a slow running filter matt in great detail (calls it "Hamburg Matten-filter"). It is quite popular in "Deutschland".

Key is:

- the waterspeed, which goes through the filter and therefore defines the size of the mat
(calculate water speed in filter with this german link http://deters-ing.de/Berechnungen/Berechnungen.htm go to: Die erforderliche Mattengröße eines Hamburger Mattenfilters

- the entire filter-mat(surface) is exposed to tank - open in water- (I personally modified that for my use, to maintain water-stream in the tank and built a housing fopr it - butr the logik staid the same as the original).

- driven by simple pump, sucking away the water behind the matt. water flows with even pressure-spreading through entire matt.

I have run a test tank with many fish and a modified version of such a filter.

never cleaned, only once in 1.5 years (except vacuuming off,when doing weekly waterchange!). Water values are great! The "bacteria home" does an absolute great job. I will use this for my new tank - now doubt - test was exceeding my expectations - and that with low maintanance...

some more links to the filter






... perhaps there is an english page... I will be glad to check, in case someone is interested... also can do quick translation of key data, if someone is just building a filter...


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The Kapenta Kid
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Post by The Kapenta Kid » Sun Sep 17, 2006 7:29 pm

Here is an English translation of an Olaf Deters article on Hamburger Mattenfilters.

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