[Grah the great]

Hi everyone! When I read about using dirt as a DIY substrate component in an aquarium, the common recommendation is to use roughly equal parts dirt and inert substrate, or sometimes considerably more dirt than the inert portion. Is there any particular reason I could not use considerably less dirt, perhaps as little as 5-10% of the substrate by volume? I was just thinking that this would make cycling the tank easier while still giving some of the advantages of dirt. For reference, the dirt was going to be in a high tech aquarium and the rest of the substrate was going to be turface. Thanks

 

[Econde]

Really depends on what you want. A lot of hobbyists that use dirt, use about 1/2" then cap it with at least 1/4" inert substrate. I used about 3/4" -1" dirt then capped it with another 1" of black diamond blasting sand. Some parts of my substrate are thicker than others. Just remember to measure after you turn your dirt into mud before adding substrate. It gets considerably compact once wet.

With that being said, I think it took me about a month to cycle? I can't recall off the top of my head.

 

[Grah the great]

Really depends on what you want. A lot of hobbyists that use dirt, use about 1/2" then cap it with at least 1/4" inert substrate. I used about 3/4" -1" dirt then capped it with another 1" of black diamond blasting sand. Some parts of my substrate are thicker than others. Just remember to measure after you turn your dirt into mud before adding substrate. It gets considerably compact once wet.

With that being said, I think it took me about a month to cycle? I can't recall off the top of my head.

I wanted some of the CEC of the soil; reportedly plants also root better in soil. Furthermore, I was hoping to dry start the tank for a month prior to filling it to allow the plants and beneficial bacteria to get established sans algae, and dry starts reportedly do not work well with purely inert substrates. If I used dirt, I was thinking of mixing the dirt with turface and then cover that with a pure turface layer.

 

[minorhero]

I wanted some of the CEC of the soil; reportedly plants also root better in soil. Furthermore, I was hoping to dry start the tank for a month prior to filling it to allow the plants and beneficial bacteria to get established sans algae, and dry starts reportedly do not work well with purely inert substrates. If I used dirt, I was thinking of mixing the dirt with turface and then cover that with a pure turface layer.

Turface is very light when submerged in water. I would use sand or if you must sand and turface combined. I would put down at least 1" of inert as a cap and 2" would be better. I would put down 1/4" of soil. Trust me it will filter up into that cap a good ways.

 

[Grah the great]

Turface is very light when submerged in water. I would use sand or if you must sand and turface combined. I would put down at least 1" of inert as a cap and 2" would be better. I would put down 1/4" of soil. Trust me it will filter up into that cap a good ways.

It did not seem very light when I tore down one of my tanks yesterday :grin2: But yeah, I can make the cap quite thick...I have a lot of 1/16-1/8 inch turface lying around. I am even considering using aquasoil at this point due to all the mineralizing that many recommend doing to dirt.

 

[Econde]

It did not seem very light when I tore down one of my tanks yesterday :grin2: But yeah, I can make the cap quite thick...I have a lot of 1/16-1/8 inch turface lying around. I am even considering using aquasoil at this point due to all the mineralizing that many recommend doing to dirt.

Nah, you don't have to remineralize it.

 

[gjcarew]

Turface actually has a very high CEC, often higher than soil (depending on the soil). Soils with a very high organic content can have higher CEC than clay (think worm castings), but you're also dealing with potentially massive ammonia and nitrate spikes. Activated carbon/charcoal also has a higher CEC than clay but those are really the only two I can think of.

You just have to make sure you "charge" turface with nutrients. If you sprinkle a bunch of osmocote down on the glass before laying on the Turface you'll get all the nutritional advantages of soil but much less dirty.

 

[Grah the great]

Turface actually has a very high CEC, often higher than soil (depending on the soil). Soils with a very high organic content can have higher CEC than clay (think worm castings), but you're also dealing with potentially massive ammonia and nitrate spikes. Activated carbon/charcoal also has a higher CEC than clay but those are really the only two I can think of.

You just have to make sure you "charge" turface with nutrients. If you sprinkle a bunch of osmocote down on the glass before laying on the Turface you'll get all the nutritional advantages of soil but much less dirty.

Yeah, I did find that at one point...after taking density into account, I found that per 100 ml peat moss and turface have CEC's of 22.77 and 17.79 respectively (I did not do soil because soil is a variable product). Oddly, I found pumice to found a considerably higher CEC per 100 ml of 39.93...I wonder if I got the wrong density for the pumice? (Pumice has a CEC of 75 meq/100g)

 

[gjcarew]

I imagine it would be a tough comparison between pumice and the other two since pumice can have a highly variable density depending on grain size. If you're talking about the density of a single rock of pumice (which is also variable) you would also have to consider that the larger the rock is, the less surface area it has available for exchanging cations.

That said, ADA's powersand (at least according to Tom Barr's analysis) is essentially pumice mixed with peat moss. ADA Clear Super and Tourmaline BC are activated carbon and bamboo charcoal, respectively. So if you took a mixture of pumice, peat, and activated carbon/charcoal and charged it with either dry ferts or osmocote, you would theoretically have created a bootleg version of the ADA substrate system which by all accounts is great for growing plants. ADA only recommends a thin layer of this substrate beneath aquasoil.

Back to your original question of how much dirt to use -- Cory from Aquarium Co-op suggests just a small amount (maybe 1 cm) of dirt below a thick cap. Having recently had a thick layer of dirt capped by aquasoil, I would agree with him. Once the plants' roots reach the dirt layer, uprooting gets super messy. If you're using CO2 you're going to need to uproot plants eventually. That dirted tank I had grew plants super well, but it was also the version of tanks that was best at growing algae due to all the dirt I was constantly bringing into the water column.

 

[Grah the great]

I imagine it would be a tough comparison between pumice and the other two since pumice can have a highly variable density depending on grain size. If you're talking about the density of a single rock of pumice (which is also variable) you would also have to consider that the larger the rock is, the less surface area it has available for exchanging cations.

That said, ADA's powersand (at least according to Tom Barr's analysis) is essentially pumice mixed with peat moss. ADA Clear Super and Tourmaline BC are activated carbon and bamboo charcoal, respectively. So if you took a mixture of pumice, peat, and activated carbon/charcoal and charged it with either dry ferts or osmocote, you would theoretically have created a bootleg version of the ADA substrate system which by all accounts is great for growing plants. ADA only recommends a thin layer of this substrate beneath aquasoil.

Back to your original question of how much dirt to use -- Cory from Aquarium Co-op suggests just a small amount (maybe 1 cm) of dirt below a thick cap. Having recently had a thick layer of dirt capped by aquasoil, I would agree with him. Once the plants' roots reach the dirt layer, uprooting gets super messy. If you're using CO2 you're going to need to uproot plants eventually. That dirted tank I had grew plants super well, but it was also the version of tanks that was best at growing algae due to all the dirt I was constantly bringing into the water column.

If I knew the density of horticultural pumice, this would be that much easier...anyhow, thanks! I may just go with an inert turface and/or pumice substrate after all...my other two planted tanks are dirted, and that dirt does indeed make a mess whenever replanting occurs.

EDIT: I found the weight of a given volume of pumice! https://www.generalpumiceproducts.com/shop/18-size-minibag

They mention that their 7 cup bag of their 1/8 inch pumice (the most appropriate size for a planted substrate) was about 2.5 pounds. Calculating that out gives a density of about .682 gm/ml for 1/8 inch pumice; this gives an even higher CEC of about 51.19 meq/100 ml (more than twice that of an equivalent volume of peat moss and about triple that of turface). That's fantastic. (I calculated the CEC based on volume because that is what matters in an aquarium or most other spaces...having a better CEC per mass matters little if getting that mass takes too much space). Pumice would probably float at first, but that could easily be solved by capping it.