Sphagnum moss as filter media

Simon Cole

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I want to try adding some sphagnum moss to my external filter into a new scape for some five-banded barbs (Puntius pentazona). I have heard that this will slightly drop the pH. My tap water pH varies between 7 and 8, so this would be very welcome. Has anybody tried this?

I know there are several good scientists in the society. Does anybody know the chemical released by sphagnum moss that is responsible for creating mildly acidic conditions? I presume this is an active compound found in living moss rather than something that is produced through decay. Could anybody give me the heads up on this?

Kind regards,
Simon
 

dw1305

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Hi all,
Does anybody know the chemical released by sphagnum moss that is responsible for creating mildly acidic conditions? I presume this is an active compound found in living moss rather than something that is produced through decay. Could anybody give me the heads up on this?
It is a combination of effects, because sphagnum peat only forms in <"ombrotrophic"> mires ("rain fed mires") it has a very low "base percent saturation", and all the initial cation exchange sites are filled with protons (H+ ions), these are then exchanged for multivalent ions (like Ca++) in the tank. The humic acids and tannic compounds in the peat will chelate some metals, again softening the water. The moss also secretes "sphagnan" an oxopolysaccharide polymer that is mildly acidic, and thought to be responsible for a lot of the <"anti-microbial properties of peat bogs">. It doesn't matter whether the moss is alive or dead for these activities to happen.
.........Sphagnan is a complex, pectin-like material which is covalently linked to cellulosic and amyloid-like chains in living Sphagnum moss, but slowly liberated by autohydrolysis into the ambient water as the dead moss is converted into peat. It is a precursor of aquatic humus from Sphagnum peat, and the tanning of adventitious collagen in animal remains is only one manifestation of the continuous incorporation of ammonia, aminoacids and polypeptides from a wide variety of sources into the structure of the humic acid molecule. Sphagnan can also suppress microbial activity by reacting with exo-enzymes and sequestering essential, multivalent metal cations........
The problem with all of this is that these effects are easily over-whelmed by water with lots of divalent cations. If you have really hard water (lots of Ca++ ions in solution and a large reserve of buffering) then as H+ ions are swapped for Ca++ ions the water will constantly replenish the Ca++ (and HCO3- ions) in solution from the reserve of buffer.

cheers Darrel
 

zozo

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I've experimented with it in the past, with adding a bag of dried sphagnum as temporary filtermedia.. But since it is a dead dried plant tissue it finaly will melt if constantly submersed. Same for if you can get your hands on life sphagnum, ive tried to use this too as substrate for emersed growth in open top aqaurium and it's pretty tough to keep this alive in mineralized and fertilized tap water. Anything submersed and dead will finaly melt away as any other dead plant tissue will do. After a while all is dead and melting, it will finaly deplete from the good stuff it relases and likely only creating extra unwanted bioload after that.

If it ever releases enough to change water parameters is depended on the initial water parameters in buffering capacity. I have relatively soft water regarding Calcium Gh 4 and a tad higher in Carbonates Kh 10.. My low tech setups easily shoot up to Ph 8.5 when plant metabolisme is highest. I never managed to drop the pH with adding alledged Ph altering natural compounts releasing Humic substances, Sphagnum, dried leaves, alder cones, filter peat, bog wood name it i've tried about all and it didn't change zip. Once i tried bog peat and doubled the recomended dosage, it made my water dark brown but nada change in Ph. I'm not sufficiently educated in chemics to give explanation why.. It likely is what @dw1305 - Darrel points out, i have to much buffering agents in my tap water that nutralizes anything mildly acidic on the fly.

It obviously lowers Ph in some cases since the story already goes around for ages that peat and leaves and cones and bogwoods do.. Likely when you have extremely soft water very low in Kh, i guess. I actualy don't know, because for my tap water it simply doesn't. For me it's what you see is what you get.
 

Simon Cole

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Thank you Darrel, Edvet and Marcel for your great replies. There are clearly quite a few pros and cons. I came across an interesting study that mentioned that sphagnan (aka. 5‐KMA) in its sodium form at neutral pH had no antibacterial activity and lost its ability to buffer. It is often described as a weak buffer, which follows on from your point Darrel.
Marcel - I was very interested to find out that it melted in your filter. It seems to me that there might be acidic and low nutrient water conditions that might prevent melting, but at this pH the antimicrobial impact of sphagnan could potentially eliminate biological filtration and plants would struggle.
In terms of promoting fish health, I do not believe that the antibacterial properties extend beyond the general impact of weak acids. I am far more interested in the use of Terminalia catappa for that purpose.
 

zozo

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Marcel - I was very interested to find out that it melted in your filter.
Never used it that long in the filter. But noticed the living sphagnum i used as plant substrate in the aqaurium that was permanently submersed, it died and turn into slimey mush in a few weeks. :) The normal dried sphagnum fibre available in the trade is sourced from fresh living sphagnum as well. I thought than obviously this will happen to it in the filter too.
 

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