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Does tannin water 'go off'?

UrbanDryad

UrbanDryad

Member
Joined
28 Aug 2023
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76
Location
Brighton
On Friday evening I boiled a beautiful piece of wood to sterilise it, and elected to keep the tannin water. It's been sitting in the kitchen in a covered pot until this morning, when I removed it and put it into bottles. There was some amount of scum on the top, which I removed. It hasn't yet been dechlorinated, and I'm probably not going to put it in an aquarium right away. Should I keep it in the fridge, or is room temperature fine? Has it already been out in warm weather for too long to be safe? It feels like a useful thing to have on hand for blackwater setups and general fish health, but obviously only if it's actually safe!
 
UrbanDryad said:
It hasn't yet been dechlorinated
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It has. By boiling.
UrbanDryad said:
Should I keep it in the fridge, or is room temperature fine?
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These compounds degrade primarily by light, esp. UV part of the spectrum.
UrbanDryad said:
Has it already been out in warm weather for too long to be safe?
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The wood probably released not only relatively stable organic compounds (lignin, tannins, humic substances) but also others, which may be attractive for various microbes.
UrbanDryad said:
It feels like a useful thing to have on hand for blackwater setups and general fish health, but obviously only if it's actually safe!
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Safety not guaranteed. Me, I would stick with commercially available black waters.
 
MrClockOff said:
Hi there

I never had blackwater fish tank but if I would want to add tannins I would make the brew fresh from alder cones. They are available for free in the parks and super easy to prepare.

Cheers
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I'd be concerned about potentially introducing pesticides or similar if I were to gather materials from a park?
 
There is this

Are these aquatic snake oil products?

Just for information, there is liquid carbon which is based on glutaraldehyde like product. But there are now other which are based on Citric acid, citrates, and other components, more natural, without glutaraldehyde. Some examples Dennerle Elixier Bio (don't confuse with Dennerle Carbo Booster...
www.ukaps.org
 
I appreciate the advice about gathering alder cones and acquiring blackwater extract, but would also definitely appreciate more opinions about whether the tannin water I have now is safe to use :) I try not to waste anything if possible!
 
UrbanDryad said:
but would also definitely appreciate more opinions about whether the tannin water I have now is safe to use
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I can contribute a personal experience with something similar - homemade peat extract. I took care to use clean Baltic white peat without any gardening additives. Prepared it in similar way like you - I warmed (almost boiled) a glass can full of RODI water with some peat and then filtered the water. Repeatedly, I've prepared several liters of the brew. Nicely brownish, I'd say a "black tea" colour.
Then I applied it in a tank which I intended to make a bit "blackwater", plus to push pH somewhat lower. The result: I've introduced some easily degradable dissolved organics, which lead to light bacterial bloom, and some sensitive plants reacted very negatively; in fact, I've lost some of them.
So, I don't know what exactly happened, what exactly was the reason of the failure. But I believe it is a good example documenting that such negative results may happen.
 
If I remember correctly there are certain enzymes in peat that can harm plant tissue (beta-glucosidase possibly). It would have been during a lecture by somebody like Professor Chris Freeman, so I checked and there is a paper he co-authored <here> that explains the chemistry a bit. Perhaps heat treatment can accelerate the liberation of these enzymes into solution; or perhaps not and it is in fact the reverse - that they become permanently denatured during heating.
 
Simon Cole said:
there is a paper he co-authored <here> that explains the chemistry a bit.
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Thank you a lot. It's revelatory to me in many respects, as well as incomprehensible in many more. In general, I considered peat a kind of "final product". Now it seems that many processes are reversible.

Yet for us, laymen, what is the practical implication? What do you think, par example, on peat layer beneath sandy/gravel sediment (substrate)? This is sometimes recommended for a group of plants (as well as fishes) loving strongly acidic black waters. Is it better or worse than adding commercial or homemade extracts to the water column?
 
@_Maq_ Peat can go through a lot of processing. Old formula Jack's Magic was heat-treated, sterilised, and stabilised, and I've got a feeling they might have even rinsed it at some point - but I don't think it would give you very much black water. I am guessing that plants living in tropical blackwaters are exposed to tannins leaching through the woodland floor. These waters contain lots of humic acids, but they aren't really similar to the chemistry of peat, and the tropical flooded or dry soils are also very different. The raw peats people use to alter water chemistry and stain the water must be leaching an awful lot of organic molecules - I don't really know what the chemistry would end up as. I have seen alder cones - and they seem like a better option, but I can't comment because I have no experience with blackwater tanks.
 
I’ve often filtered through moss peat. Never really had any problems with plants or fish, quite the opposite. However, I’ve also lived in hard water areas so in terms of water pH etc I doubt it made much of a difference.

Anyway, I don’t think a bottle of tannin extract will go off as such. And should be safe to store for a good while. If you’re worried you could test a suitably diluted solution with a daphnia bioassay.
 
This is fascinating, thank you all 😍I love the dedication to science over rumour here, I'm so glad I joined this forum 💙
@Tim Harrison A daphnia bioassay is an excellent idea, although I'd need to a daphnia culture first! But that would be useful for live foods as well, so maybe I'll look into that... any tips for starting up a culture and bioassaying outside of lab conditions? :)
 
There is some info here. But I think it’s pretty simple.


Daphnia are often available as live food from LFSs. They often turn up in my water butts by themselves. Dispersal in Daphnia is usually characterised as being driven by the passive transport of ephippia (long-lived resting eggs). Either way they’re easy to keep alive

www.ukaps.org

How to: Clean, easy and highly nutritious greenwater culture for Daphnia and Moina.

Recently I asked on here whether anybody had experience cultivating the green algae Chlorella vulgaris in freshwater for use in feeding Moina macrocopa cultures. The species is often used in saltwater phytoplankton systems, and is the preferred food for industrial scale Daphnia and Moina...
www.ukaps.org

Then just isolate a sample and add whatever it is you’re testing to that sample, and observe the reaction.
 
UrbanDryad said:
I appreciate the advice about gathering alder cones and acquiring blackwater extract, but would also definitely appreciate more opinions about whether the tannin water I have now is safe to use :) I try not to waste anything if possible!
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Whether the tannin water is safe for your tank really depends on the type of wood its come from. If you know the wood is safe to put in an aquarium, then it's likely the tannin water is fine too.

As others have said, 'collectables' from parks and woodlands are a good alternative source for tannins. Alder cones, oak and beech leaves, or purchased catappa leaves and bark all work as will mopani wood from a LFS, Rooibos tea also works well. Tannin tinted water can be quite difficult to maintain in a reasonably lit aquarium though, as the brown tint breaks down rapidly on exposure to light.
 
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