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[APD] RE: RFUG
> Subject: [APD] African Planted Tank and RFUG
> To: aquatic-plants at actwin_com
> I have been leaning towards using a RFUG in my bosses 75 gal African tank
> work. I read about them in the archives as well as some of the posts Tom
> Barr made to my questions back in Jan. '04. He said that the flow should
> slow, on the order of 1 GPM. I have been reading Diana Walstad's book,
> Ecology of the Planted Aquarium. I learned that Ferric Iron is reduced in
> the substrate to the plant useable Ferrous state under near anaerobic
> conditions. If I use a RFUG, even with the low 1 GPM flow, I wouldn't
> any anaerobic area's in the gravel, correct?
The pattern of flow that comes out leaves regions similar in shape to egg
crates that are unaffected by the RFUG., so called "dead spots".
The other issue is with the poroisty of the gravel etc, if it has high
surface area etc, then it possesses lots of internal anaerobic zones that
can help reduce iron.
But to say plants cannot use Fe3+ is wrong, they can and do reduce the iron
all by themselves. They have to remove the chelator such as gluconate or
ETDA to use the liquid iron folks add also.
Fe3+=>Fe2+ is not a cut and dry state. At 200-300mv Fe3+=>Fe2+ and this is
also influenced by pH since the Eh and pH are related.
It does not mean 100% no O2 or 100% O2.
Reduction oxidation has a scale, it's not black and white.
Plants can do their own thing and the grain's internal spaces can also play
a huge role.
> I guess my question is: Why even use a RFUG? Tom once did on an African
> tank. I must have missed the reasons (or forgot them) for using one
> somewhere. Can anyone provide some of the positive factors in using
> Can anyone give some of the drawbacks in using RFUG's? Remember, this is
> primarily a planted tank. The fish are very important to my boss.
More surface area for bacteria/cycling(think about sand filters for
example), less mulm accumulation, good for plants.
> I originally was going to plant my plants in pots buried in gravel or
> This would shield them from digging fish. I am now leaning towards
> some directly in the gravel and forgoing the pots as I have decided to go
> with mostly small non digging Julidochromis, Neolamprologus, and
> Labidochromis. Anubias and Java Fern will be growing on the rock walls. I
> bought four bags of Onyx sand to use in the pots, but now I am wondering
> I should make a three product mix with the Carib Sea African Cichlid
> Mix/Profile Aquatic Plant Soil that is in the temporary 20 H set up in my
> bosses office. From what I have been reading it appears the benefits of
> using Onyx for its Iron and other nutrients will be best realized where
> anaerobic conditions occur. Am I correct?
Well this gets back top the internal spaces in the grains of Onyx.
I'd use all onyx for an AF tank.
The color looks good with many of those fish.
> Thanks for your help,
> Jerry Smith
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