Mesh bags vs plant roots

[UrbanDryad]

A piece of advice I've seen in several places is to put aquasoil (or other nutrient-rich substrates) inside mesh bags, to prevent it mixing with decorative caps of sand/gravel. I can see the benefit in terms of aesthetics, but I can't help but wonder if it impedes root growth (due to reduced space) and/or the ability of root-feeding plants to access the benefits of the aquasoil. I had a look through the forum and couldn't see a thread specifically addressing this. I'd love to know what your experiences with this have been!

 

[AlecF]

This! Yes, I rather regret using them. My soil mix includes clay and that may be an issue, as I think the soil has hardened. I have a low tank and can't afford a deep layer of sand. I find it hard to plant into the bags and plants tend to go in best in the gaps between them. I have a separate tank with plastic divider sheets, which I found better, though when these ride up all you can do is add sand. I understand the advice to use bags, but I think it can be problematic and it depends exactly what soil you use, and how that soil may alter over time, and what type of sand you have. I've also had issues with the slack in the bags bunching up and being visible, and hard to conceal with sand. It's one of those things that sound simple, but there are good and bad ways to do it.

 

[Tim Harrison]

I don't think I'd opt to use mesh bags filled with actual soil, maybe AS. But only under around 40mm of capping substrate. I've usually used a plastic mesh divider with 1-2mm gaps. Roots naturally pass through it unhindered via a process known as geotropism. I've used filter bags and nylon tights filled with either pea gravel, molar clay, or pumice, to bulk out the substrate to create banks covered by soil, capping substrate or AS, though. That's worked fine so long as the capping substrate is thick enough.

 

[UrbanDryad]

I don't think I'd opt to use mesh bags filled with actual soil, maybe AS. But only under around 40mm of capping substrate. I've usually used a plastic mesh divider with 1-2mm gaps. Roots naturally pass through it unhindered via a process known as geotropism. I've used filter bags and nylon tights filled with either pea gravel, molar clay, or pumice, to bulk out the substrate to create banks covered by soil, capping substrate or AS, though. That's worked fine so long as the capping substrate is thick enough.

Oh, that's smart! What kind of mesh divider? Knitting mesh? Or something bigger like egg crate? And yeah, I've done mesh bags with lava rock to create levels, but that definitely felt different as there's still enough substrate for the roots

 

[UrbanDryad]

This! Yes, I rather regret using them. My soil mix includes clay and that may be an issue, as I think the soil has hardened. I have a low tank and can't afford a deep layer of sand. I find it hard to plant into the bags and plants tend to go in best in the gaps between them. I have a separate tank with plastic divider sheets, which I found better, though when these ride up all you can do is add sand. I understand the advice to use bags, but I think it can be problematic and it depends exactly what soil you use, and how that soil may alter over time, and what type of sand you have. I've also had issues with the slack in the bags bunching up and being visible, and hard to conceal with sand. It's one of those things that sound simple, but there are good and bad ways to do it.

Thanks for sharing that Do you construct the divider sheets yourself, or buy them pre-made? And do you attach them to the tank, or just keep them in place using the substrate?

 

[Tim Harrison]

What kind of mesh divider?

Something like this. https://www.amazon.co.uk/Gardman-Gr...ding+gardmans&qid=1565549090&s=gateway&sr=8-1

 

[ElleDee]

Something like this. https://www.amazon.co.uk/Gardman-Gr...ding+gardmans&qid=1565549090&s=gateway&sr=8-1

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Do you secure that down somehow or just use the cap to hold it down?

 

[Onoma1]

I use mesh bags with John Innes Number 3 / old substrate (aquasoil / sand). I sometimes add fertiliser tabs.I initially bought bags with plastic zips from ebay more recently I use the mesh fruit bags that lidl sell. I cap them with enough sand to plant in. It works wonderfully. Plants root into the bag and can be moved when rescaping with the bag allowing a modular system for moving crypts and other deep rooted plants. I also find that nutrients don't leach from the bags and that the roots rapidly penetrate allowing gaseous exchange. I found the downside of the single piece of mesh being that the roots were beneath the plastic and the growing tip was above. When I wanted to rescape I would have to cut the plants away losing a good number in the process.

 

[Mr.Shenanagins]

I’m a mesh bag user with terrestrial soil. I have zero issue with plants reaching the soil and penetrating the mesh. I will say that I did not stuff the bags out, and I also did add some grit to the soil so that to potentially cope with anaerobic conditions. I copied @Tim Harrison example of using the mesh netting initially, I just found the bags to be more useful for me when setting up the scape and keeping the mess to a minimum. Both ways work wonderfully

 

[AlecF]

I use a more solid grid than Tim shows; his looks better. I haven't had problems with the plants rooting through it. My two problems were using zip bags that were too large, and having bags flapping around, and the fact that I think the clay powder, which I didn't bake, solidified with the John Innes soil, and that I haven;t the depth available that Tim has. Some of this just beginners stupidity. The main thing I wish I had done is find a system to fix the bags and sheets to the bottom, so they don't ride up through the sand. Possibly a thin layer of gravel. It just shows how important it is to have the right kind of each element. Tim's arrangement is so neat!

 

[Tim Harrison]

Do you secure that down somehow or just use the cap to hold it down?

Just a good layer of capping substrate, 30-50mm. I often used pool filter sand, which worked very well.

My two problems were using zip bags that were too large, and having bags flapping around, and the fact that I think the clay powder, which I didn't bake, solidified with the John Innes soil,

Some terrestrial soils and composts do solidify in the process of becoming aquatic sediments. I think what happens is the organic matter breaks down and is used as nutrients by plants. This eventually leaves the bulk of clay particles behind which clump together and solidify.

I try to avoid this by adding a lot more organic matter, and often grit, gravel and/or sand. I've also used molar clay. Others like @Onoma1 above use old AS and add root tabs for good measure as well. I guess it doesn't matter really so long as the material isn't harmful and improves structure and prevents the sediment from solidifying.

I think there is definitely something to keeping nutrients locked up in the sediment, feeding the roots and using the water column to perhaps folia feed micros. Especially if you want to experiment with relatively high light intensity and grow plants without CO2. And on that note additional organic matter will help since a byproduct of mineralisation is CO2.