Peat substrate?

[daizeUK]

I've decided that I want to try a Walstad soil-based tank but I'm getting confused about what substrate to choose.

I've read Troi's introduction to soil substrates and he recommends peat due to the release of carbon-reach humic substances, if I've understood it correctly. Peat also interests me because my water is hard and alkaline (pH 8.2, GH 15+) and it would be nice to lower that slightly. I don't want to use John Innes or anything similar with lime in it that would raise hardness further.

I've read Aaron Talbot's guide to mineralizing topsoil and he specifically recommends NOT using peat although I'm not clear why. The mineralized route sounds equally interesting due to the reduced ammonia/algae and more stable substrate it provides.

I understand that Diana Walstad has used peat in tanks herself but does not recommend it due to problems she experienced with iron toxicity.

So I'm getting confused about these conflicting avenues of advice.

Apart from the acidic interaction with iron, is there any good reason not to use peat?
What do peat-based tanks do for iron supplementation, if anything?
Can topsoil (mineralised or otherwise) provide comparable levels of carbon for plants? Ideally I'm trying to achieve a tank where no carbon supplementation is necessary.

 

[dw1305]

Hi all,

Peat also interests me because my water is hard and alkaline (pH 8.2, GH 15+) and it would be nice to lower that slightly.

It won't have much effect on your water hardness. To have any effect it has to "white" sphagnum peat (formed in an <"ombrotrophic mire">), then it will exchange H+ ions for cations like Ca++ (multivalent ions are more strongly bound than monovalent ones), but it is cation exchange, meaning that the exchange sites will soon be filled with Ca++ ions and any softening effect will cease.

I've read Aaron Talbot's guide to mineralizing topsoil and he specifically recommends NOT using peat although I'm not clear why. The mineralized route sounds equally interesting due to the reduced ammonia/algae and more stable substrate it provides.

If you mineralize soil you have oxidised all the organic matter (carbon compounds) and left the mineral component of the soil (hence "mineralized"). Peat is almost pure carbon (which is why it <"burns when dry">) and has accumulated where nutrient and oxygen levels have limited bacterial decomposition. All the peat will oxidize into CO2 during mineralization.

I understand that Diana Walstad has used peat in tanks herself but does not recommend it due to problems she experienced with iron toxicity.

If your substrate has has areas which become anaerobic (negative REDOX values or reducing conditions) then iron will become available. This is usually a good thing, but you can have too much of a good thing and one of the problems for plants that grow on peat bogs is iron toxicity.

Can topsoil (mineralised or otherwise) provide comparable levels of carbon for plants? Ideally I'm trying to achieve a tank where no carbon supplementation is necessary.

Not really, if you have organic matter in your substrate it can definitely provide some CO2 to the plants. Problems may occur if you have low levels of water circulation at night, when oxygen depletion and high CO2 levels may occur.

I use different approach to maintaining CO2 levels and it is a bit of a counter-intuitive one. I like a lot of water turn over (to maintain a large gas exchange surface), this means that levels of CO2 and oxygen more closely match atmospheric levels. You will never have much CO2 in the water, but during photosynthesis it should ensure some CO2 is always available to the plants.

cheers Darrel

 

[Daneland]

Is aqua compost any good?

 

[sciencefiction]

Can topsoil (mineralised or otherwise) provide comparable levels of carbon for plants? Ideally I'm trying to achieve a tank where no carbon supplementation is necessary.

My answer would be yes as I used mineralised soil myself, no supplements needed at all even if the soil is mineralised.

There's plenty of organics to produce carbon for the plants to grow. I experienced really fast and healthy growth so I wouldn't worry about depleting organics if mineralising the soil. A proper mineralisation/soak process will ensure the soil is reduced to a very "pure" soil that doesn't cloud for long when replanting afterwards. Plus there will be nutrients in the soil in a form immediately available to plants without the wait and trouble period.

Organic matter in the soil is not a problem, it builds up back again over time so I don't think there'll be ever lack of it. But too much of it at the start can cause problems, some of those that Darrel mentioned. The other problem is algae outbreaks which just doesn't seem to happen with mineralised soil providing other factors are balanced plus you can add your stock sooner as ammonia production is minimised.
I think there's no need to have peat, not for the purposes of making the water acidic. If you don't do water changes, the water will become acidic over time. Diana and Aaron Talbot suggest some form of Ca/Mg base in the substrate or water to keep the tank stable, otherwise it will go too acidic so having hard water is not a negative in such a tank setup. If you want soft water, then RO sort of mix is the only way.
Aaron Talbot also suggests a bit of clay mixed into the substrate which will help the water column stay clearer and also helps the soil settle faster because of the properties of the clay. The clay will act as a free iron supplement as well long term.
I have iron deficiency problems in all my tanks bar the soil/clay ones but that's because my water is hard and the iron doesn't stay in solution in the water column when dosed but the soil/clay combo substrate counteracts that and I have no problem with iron in these. So there are two sides of the coin I wouldn't mind myself some more iron. Yours could be an issue too if you have hard water. Also, I found out that clay pebbles as media in the filter provides a good amount of iron for me too in a tank with plain sand but obviously doesn't have the extra benefits of pure unbaked clay for keeping a very clear water column/purigen like type.

But it can be done without mineralising the soil too but ensure plenty of oxygen at the start otherwise the soil may go anaerobic and wipe out plants and stock and it's hard turning back from there. This doesn't happen each time but if one doesn't have enough plants and oxygenation at the start, it sort of does each time. I've seen plenty of "Diana Walstad" types having a rough starts as the users were inexperienced and followed the "not too much surface movement" advise in order to avoid loss of carbon. Later Diana revised and advised the more oxygen, the more carbon production as the bacteria that one needs in the substrate for carbon production relies on oxygen. The anaerobic decomposition is the one to avoid because it produces harmful other gases instead.

 

[sciencefiction]

Here is my time lapse with mineralised soil. Please excuse the "aquascape" as I literally just planted and didn't do much changes afterwards, just wanted to get it going as my plants arrived all in poor state having been stuck in the post.

4 months later and many trims.

 

[daizeUK]

Darrel - many thanks for your detailed reply.

I understand about the surface agitation method of maintaining low levels of CO2, in fact I try to employ this method in my current liquid-carbon dosed tanks. Unfortunately one of them is a Juwel Lido 120 which is nearly 2ft deep so I struggle to get enough CO2 down to substrate (especially combined with the hard water). This is one reason why I'm hoping to use a soil substrate to provide additional CO2.

ScienceFiction - thanks for the great reply. You answered what would have been my next question, which was if organic substrates stop providing CO2 once they have completed mineralizing in the tank. You also helped me to understand why clay is such a useful additive.

I admire your tank - abundant healthy-looking plants is what I want. Both of my tanks are lidded which limits what emergent/floating plants I can have and I hope that will not be a major drawback.

I think I would like to try the mineralisation route. Now I need to choose a topsoil, preferably one that will not add much hardness if possible. I already checked my garden soil with the soap test and it was still cloudy after 24 hours, so I interpreted that it has too much colloidal clay to use in the tank unfortunately.

Cheers,
Daize

 

[sciencefiction]

I didn't do a soap test with mine as I didn't have much choice with soils but when mineralizing the soil and soaking it prior to each dry cycle, it hardly settled very fast, especially at the start. I'd leave it for 24 hours or so at the start, whatever hasn't settled by then I would pour out carefully, especially the floating on the surface bits, as that will happen in the tank too when disturbed. You lose quite a bit of soil this way but you end up with something that settles fast. The last few times then when soaking it results in soil that will settle down in an hour or two while in the container but you'll never get a pure clean water. I also sifted mine in the end, found all sorts of funny stuff like pieces of glass. I used a kitchen strainer. When it's mineralised after the 5 sessions, it totally changes how the soil looks when dry. The feel between my fingers was like sifting powder.

Here are some pictures I took then:

New soil:

Soaked for the first time, disgusting stuff. Eventually it didn't look anything like this when nearly mineralised but I didn't take a picture.

Mineralised(5 soak and dry) and sifted and tested by my dog

5-10% clay added

Water added and mixed before putting in the tank I posted above.

 

[daizeUK]

Thanks SciFi. I read your 'Disaster!' journal last night. Sorry to hear that you had such problems with your lighting. I wonder how the tank would have progressed without all the hiccups!

I noticed that you used a mix of Homebase and B&Q topsoils. I was leaning towards Homebase as there are some reviews complaining that the B&Q stuff is poor quality and it seems to have a high percentage of 'green' compost.

Now you've got me thinking that a shop-bought topsoil would be no better than the stuff in my garden, if yours was cloudy and the process of soaking and pouring naturally clears it anyway.

This was the result of my soap test on garden soil - would you say that your soil mix was any clearer than this?

Edit: I forgot to ask, which clay did you use please?

 

[sciencefiction]

Nope, my soil was not clearer at all at the start. It was gross.

Give me a second and I'll tell you the name of the soil I recommend.....It also doesn't boost the Gh too....

 

[sciencefiction]

If you want to use topsoil, use the homebase topsoil not the B&Q topsoil version as the latter was extremely dirty and contained twigs and stuff more than soil. But either way you'd have to do the work to "clean" the soil during soaking by taking out the floating stuff.

None of these have any effect on the Gh, KH, TDS, etc....

Homebase:
http://www.homebase.co.uk/en/homebaseuk/homebase-top-soil---25l-648091

And if you want a peat containing one, although it says "peat free", I'd recommend this one below, Verve grow your own fruit and vegetable planter, does as well as the homebase in a tank and is clean enough.

http://www.diy.com/departments/verve-grow-bag-27l/257682_BQ.prd

 

[sciencefiction]

The verve vegetable planter mineralised setup in a bowl I did last summer and forgot about it. There's no heater, no water changes done only topping up and this spring I noticed that not only I had it contaminated with cherry shrimp by accident, probably when adding the plants or topping up, but I saw a berried female as well and quite a few grown up shrimp in there. I used the verve fruit and vegetable planter in a small tank, but non mineralised and it had a few algae outbreaks over the life of the tank(mostly green algae) unlike my other tank so I'd use it again, but mineralised only. This bowl struggled through the winter without sunshine so not in best shape yet but is recovering, now the sunshine is back.

 

[PARAGUAY]

Is aqua compost any good?

Just a little input I can add as I think I will try Aquatic Compost for ponds at some stage myself.,There is a excellent article by Tim Harrison,a science lecturer, on hybrid energy planted tanks wherby you can take or leave the addition of pressurised CO2 by the use of various composts EG with grit mixed with loam,using on its own sphagnum moss peat and on its own Aquatic Compost for ponds,his experiments show brilliant results try to check it out ,a two part article in PFK August 2012.

 

[Tim Harrison]

It's great to be able to get an angle on all the science behind why this and that method works and that one not so. Each experience is different, in my case from one tank to the next. But I don't think you need to worry too much about the details, I always try to keep it stupidly simple. Keep the soil layer relatively shallow, and allow for plenty of flow and distribution and it usually all works out regardless of water chemistry, or soil type - clay:mineral: organic ratios or whether you mineralize in situ or use MTS.
If after all you still experience some deficiencies, just chuck some fertz in...the amounts needed in a soil tank are so small that its inexpensive and easy. If you use floaters, try Darrel's "Duck Weed Index" as a guide. I grew floaters in covered tanks back in the day and they usually did fine.

P.S. Thanks PARAGUAY for the compliment regards the article in PFK...Troi is a pseudonym you can also find the article in the tutorial section

 

[daizeUK]

If you want to use topsoil, use the homebase topsoil not the B&Q topsoil version as the latter was extremely dirty and contained twigs and stuff more than soil. But either way you'd have to do the work to "clean" the soil during soaking by taking out the floating stuff.
None of these have any effect on the Gh, KH, TDS, etc....

Thanks, that confirms what I was thinking. I'm going to have a go at mineralising my garden soil and see how it fares, keeping Homebase topsoil in mind as a backup.

I have a raised bed which I was going to dismantle anyway (a disused rockery) so I have plenty of topsoil going spare. It should be free of pesticides and chemicals as I've never really used them, certainly not in the last 5 years at least. I'll see if I can get a pH reading of my soil but I expect it will be fine.

If after all you still experience some deficiencies, just chuck some fertz in...the amounts needed in a soil tank are so small that its inexpensive and easy. If you use floaters, try Darrel's "Duck Weed Index" as a guide. I grew floaters in covered tanks back in the day and they usually did fine.

Thanks for the input Troi, I'll check that out. I currently grow Salvinia in my covered tank and it's always put out lots of very small leaves, spreading rapidly but with older leaves dying off at a rapid rate too. It never looks very healthy due to the constant die-off. This was back when I was EI dosing with plenty of water column ferts too.

 

[PARAGUAY]

Located the tutorial Troi, cant believe I missed it on here,my son has decided to visit and help himself to a pile of back copies of PFK (total chiclid geek appreciates but not totally into aquascapes)so I can still refer back