# Organic compost query



## Kezzab (10 Apr 2018)

Hi - looking for some advice/others experience. Contemplating a rescape of my 90cm, sumped, tank. My thinking was to transfer all fish to the sump (approx. 60ltrs) temporarily and turn that into a closed loop, then sort out the display tank.

If i used 100% organic garden compost, capped with sand, as the substrate then planted it up, how long (very roughly) do you think i'd need to leave it before hooking it back up to the sump and moving fish back in to the display tank? I appreciate that's a bit "how long is a piece of string"!

Does that make any sense?

K


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## dw1305 (10 Apr 2018)

Hi all, 





Kezzab said:


> If i used 100% organic garden compost, capped with sand,


Why do you want to use garden compost? and is it from your own garden compost heap?

If it is from your own compost heap? I would only use it very sparingly, if it isn't I wouldn't use it all. 

The problem would be that green waste compost is very rich in soluble salts (basically you've taken a large volume of green waste (grass cuttings, vegetable peelings etc) and then a combination of invertebrate shredders, fungal decomposers and  bacteria have reduced the volume by (mainly) removing the carbon and nitrogen. Usually nitrogen availability limits decomposition, but if you add nitrogen decomposition will continue, and if you don't have a lot of woody waste (or cardboard) in the mix you end up with a small amount of very salty, alkaline, organic matter. 

You don't tend to get thermal decomposition in home compost heaps, but commercial producers get their green waste up to ~75oC which gives you a quicker "compost", but further concentrates the salts. You also get a lot of wood chips in these.

The compost won't have much in the way of CEC, because it doesn't have any clay or structural carbohydrates in it. I use a bit of persistent leaf litter (Oak or Beech) and a small amount of clay in my tanks (they are 90% sand substrate). 

cheers Darrel


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## Kezzab (10 Apr 2018)

Thanks Darrel, that's helpful. It was commercial organic compost and i'd thought about using it because i have it!

Perhaps the simplest/lowest risk thing would just be to use sand and some old JBL substrate i have lying around.

Thanks


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## Tim Harrison (10 Apr 2018)

You'll be fine using aquatic compost capped with gravel; it's the substrate used to plant up pond tubs with lilies, and marginals etc. I've had very good results with it in the past. I've also mixed it 1:1 with moss peat and that works well too. That way you get a substrate that has just enough nutrients to encourage plant growth without causing too much of an ammonia spike. Also, as the organic matter decomposes it releases some CO2, which is always welcome. 
My soil substrate tanks have always cycled in a week or two, but that's when they are hooked up to a filter with regular and substantial water changes. Hobby grade test kits have their limitations, but I use them to gauge how far along the cycling process is. When ammonia is reading zero, or thereabouts, it gives me a rough idea of when to add the critters, which I do a few at a time, so as not to stress the system too much and cause another ammonia spike. All the info you might need is here https://www.ukaps.org/forum/threads/the-soil-substrate-or-dirted-planted-tank-a-how-to-guide.18943/


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## Kezzab (10 Apr 2018)

Thanks Tim, what's the distinction in composition between organic terrestrial compost and aquatic compost that makes one bad and one OK?


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## Tim Harrison (10 Apr 2018)

Well I guess most have some organic matter in them. What is important is the composition of that organic matter content as Darrel mentions above. The worst case is that some organic matter could prove toxic.

The composts often recommended, like pond compost, John Innes, and Miracle Grow have been tired and tested and are not only safe to use but will grow plants well. Pond soil for instance is mostly loam, including some organic mater - usually peat - which gives it a high CEC so it will hold nutrients that will be available to plant roots.


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## Angus (10 Apr 2018)

What about mineralizing the organic compost  Kezzab  mentioned? would that work? i have never done a dirted tank myself, so this is an interesting read.

Also regarding @dw1305 's post, when you say green waste composts are you including raw woodchip and mass green waste based composts with minimal grass addition in this conclusion?


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## dw1305 (10 Apr 2018)

Hi all,





Kezzab said:


> Perhaps the simplest/lowest risk thing would just be to use sand and some old JBL substrate i have lying around.


If you have a garden with clay soil you can just use that. I go and get the clay I use from the green-sand to the east of us, because our soil is alkaline and I keep soft water fish. If I had suitable clay in the garden I would use that.





Kezzab said:


> terrestrial compost and aquatic compost that makes one bad and one OK?





Tim Harrison said:


> Well I guess most have some organic matter in them.





Tim Harrison said:


> I've also mixed it 1:1 with moss peat and that works well too


I think the aquatic composts have a lot more clay ("loam") in them. Moss peat is a bit different as it doesn't have any nutrients in it, it has formed in ombrotrophic (rain-fed) mires and is pretty much pure carbon. 





Angus said:


> What about mineralizing the organic compost Kezzab mentioned? would that work?


It would, but you wouldn't end up with much volume of compost and you would still have the increased salinity issue. 





Angus said:


> when you say green waste composts are you including raw woodchip and mass green waste based composts with minimal grass addition in this conclusion


It wouldn't be the wood chip or wood chip based composts, but if you made your own compost (or had a source of green waste compost without much grass in it) and had a relatively small grass addition, compared to the amount of woody waste, it would be slightly more suitable. 

I haven't ever checked, but I would imagine that municipal green waste compost made in the winter would be better than one made in the summer (when it  has more grass in it).

I get what is basically "worm worked" compost from our compost bin, I don't have much grass and the compost never really heats up. The larger bits of wood take a long time to degrade, because I don't have a chipper and it is about 50% soil, because I'm not particularly conscientious about getting all the soil of the weeds etc before they go in the compost bin. 

cheers Darrel


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## zozo (10 Apr 2018)

https://www.velda.com/pond-products/bottom-plants/plant-substrates/lelite/


> It contains blue loam and dried fenlland peat



http://www.swelluk.com/velda-water-lily-soil/

I used it last summer as base layer for a little outdoor aqaurium, first Velda Lelite, than a layer of sand and than a layer of silica gravel. It is a very consitant soil specialy based on aqautic use, i likely will leach some, but it actualy didn't realy in significantly high values. Only used patches of it at planted areas, the rest in between is sand.. It is very consistent and low in organics other than peat that is already done composting. I experienced exeptional plant growth from a few potamogeton spp. a nymphoides sp. and Lobelia. After the summer i moved it indoor under significantly less light than outdoor and the plants kept on growing relatively well. Only the lobelia and nymphoides suffered a bit from ligh deficiency. The potamogetons kept on growing like champions. One is teh sub tropical P. Gayi and must say it grew beter in this setup than it ever did in my high tech setup on inert akadama. In a hard soil like akadama it didn't run that much, in the soft clay soil the plant did spread all over the tank in weeks time and pops up in every corner.

This little tank still is set up today and running well in the cellar, next month i'll put it back outdoors again.  Looking at the plants i don't think the soil is depleted yet.

Also from a scaping side this soil is very soft but still consistent in holding shape, it doesn't have the tendency to slide if it's slooped up to the back as more loose or hard granulated soils always do without the use of supports.

I have no experience with other organic soils than this in an aquarium.. And actualy not sure if i ever will find a beter one, even without that if i had to give it a rating it gets a 9 out of 10... I think this stuff rocks and i'm definitively will use it again also for an indoor setup. I think for the € 9.- per 10 litre i will not find a beter soil and also don't feel the need to find any.. (£ 13 for the UK as far as i could find out, still pretty cheap for UK standards).



Here is a sneek peek on last summers plant growth from it.





How this will perform comming summer, will follow up in the pond section..


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## Angus (10 Apr 2018)

I want something like this for summer @zozo it's on my wishlist, might have to make my 200L tank a summer tubbin' project before it becomes an aquascape.


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