The Importance of Substrate in a Planted Aquarium

I recently have set up many lowtech tanks for clients (and myself) to do some experimenting to discover the best formula for a lowtech aquarium. Out of all of my little experiments, one thing has held constant:

SUBSTRATE MATTERS. I know that in the past I've constantly advocated for simple pool filter sand or black diamond blasting sand. Those substrates will work, but not nearly at the level that real, nutrient-rich planted tank substrates work.

I am not talking about inert substrates such as eco-complete or seachem flourite. I am talking about aquasoils, such as ADA Aquasoil, Ultrum Nature Controsoil, Tropica premium soil, and Fluval Stratum. These substrates have seriously impacted plant growth and have made keeping a lowtech tank much easier.

I am able to grow rotala H'ra in a lowtech environment with pink color! I am able to grow red ludwigia without stunting. I am able to grow hydrocotyle japan, ludwigia ovalis, and so much more, now that I've gotten a decent substrate. Not only am I able to sustain these species, but the actual growth form is much better too. I'm getting lush growth forms, decently fast growth, dense growth, and colorful growth. These plants have not done too great in a tank with just plain old sand in it.

Here are some possible justifications as to why these aquasoils prove to be better than classic inert substrates:

1) The relationship between bacteria and plant roots that are simply not present in inert substrates. Aquasoils are essentially a soil baked into a ball. Most of this soil is very clean and specially made for aquariums. In terrestrial ecosystems, there are many complex relationships between soil in the bacteria and the plant roots, which may not exist in aquatic ecosystems with inert gravel that is smooth, like sand. Providing a soil type substrate allows for those essential bacteria/plant interactions that may prove to give that unbeatable edge in a lowtech environment without the tremendous aid of pressurized CO2.

2) Plenty of space between each granule. I've noticed that the particular sand I use is very fine and has possibly been resulting in compacted areas of substrate, which have possibly killed some plants by compacting the roots. In aquasoils, there is adequate space between the granules, making planting somewhat difficult at first (especially with lighter substrates like fluval stratum), but this also seems to help the plants get rooted much faster.

3) The abundance of nutrients in the substrate. There simply is just an unbeatable source of nutrients readily available in the substrate, in which plants will not have to rely solely on water column fertilization.

*Important distinction to make: Raw soil is not a replacement for specialized aquarium aquasoils. I have used dirt in many of my tanks. In my experience, stuff like Miracle Grow Organic Potting Soil straight out of the bag with no extra processes, capped with gravel or sand, is absolutely horrendous to use. The growth I get out of this soil is on par with that of just plain inert sand. The amount of ammonia released leads to unpredictable algae blooms, and a horrible smell when taking down the tank. If you are planning to use dirt as a replacement for aquasoils, be sure to go the more time consuming route by purchasing topsoil (without perlite and large sticks!), and be sure to go through the mineralization process as well. This will greatly improve your chances of success.

Personally, I don't think that dirted tanks are for beginners, as it is quite difficult to manage if you are new to the hobby and it is exceedingly messy. I wish that I would have used these expensive (but effective) aquasoils sooner.

 

Great to hear of your experiences. How long do aquasoils retain their nutrients?

 

I have to agree. I've tried a variety of substrates for low-tech planted tanks, and anything more demanding than a marimo moss ball just does not thrive without a soil-based substrate. Their nutrients may start running out over time, but the boost that they give to a new tank is just fantastic. Root tabs simply do not compare.

Aquasoil and other granulated aquarium soils are definitely the absolute best you can use, with or without CO2. I kind of wonder if the initial decay in a newly set up tank releases CO2 into the water, because certain plants like s. repens and bonsaI rotala initially grew extremely well, whereas they are now shrinking in size and melting. Of course, this could simply be because they had less competition when the tank was more sparsely planted.

The only thing about it other than its crazy price tag is that if the tank is shallow, using a HOB filter will make the water yellow and cloudy.

I've personally had decent success with dirted tanks too, though. It helps to sift out the twigs before pouring it in. My main issue is how the decaying soil will often form gas that can rot plant roots if you don't poke the soil every now and then. Aside from that, as long as you have lots of plants in there from the outset, as well as plants that spread themselves rapidly, dirted tanks aren't very hard at all to maintain.

Would I recommend keeping anything more demanding than medium-low to medium light plants in them? No, but I believe it's a cheap and acceptable beginner's planted tank. It was for me!

 

Eco soil for garden or indoor plants will work too. No matter if you use filter or not. I really want to do Walstad tank.

 

Great write up. I may eventually go that route some day on a smaller scale (10 gallon). My major concern is when the substrate loses its nutrients and turns to mush and needs to be swapped out. That sounds like a nightmare

 

Great write up. I may eventually go that route some day on a smaller scale (10 gallon). My major concern is when the substrate loses its nutrients and turns to mush and needs to be swapped out. That sounds like a nightmare

I think this is the main question people have with soil substrates. I have read conflicting information regarding this, so it is very confusing. (I am a complete beginner, and have just started a dirted tank) Theoretically, the waste for the livestock should reinvigorate the substrate just as manure will reinvigorate terrestrial substrate. Whether that works realistically I am unsure. As stated, I have read conflicting resources.

 

Aquasoil style substrates are the only specific planted tank substrate I'll recommend apart from inert gravel / sand.

Only problem I see is the buffering being a nightmare for pH swings during water changes, not lasting very long in hard water, being messy when it's aged. That's why it's best used with RO water.

Inert is good for the life of the tank...

Nothing is ever a one size fits all.

 

Great to hear of your experiences. How long do aquasoils retain their nutrients?

To be honest, I am not sure. I have read reports that certain brands exhaust within a year, while others go strong for years on end. I think it's important to also dose the water column with ferts, because the substrates will absorb these ferts over time and retain nutrients for a longer time due to their high CEC values.

I have to agree. I've tried a variety of substrates for low-tech planted tanks, and anything more demanding than a marimo moss ball just does not thrive without a soil-based substrate. Their nutrients may start running out over time, but the boost that they give to a new tank is just fantastic. Root tabs simply do not compare.

Aquasoil and other granulated aquarium soils are definitely the absolute best you can use, with or without CO2. I kind of wonder if the initial decay in a newly set up tank releases CO2 into the water, because certain plants like s. repens and bonsaI rotala initially grew extremely well, whereas they are now shrinking in size and melting. Of course, this could simply be because they had less competition when the tank was more sparsely planted.

The only thing about it other than its crazy price tag is that if the tank is shallow, using a HOB filter will make the water yellow and cloudy.

I've personally had decent success with dirted tanks too, though. It helps to sift out the twigs before pouring it in. My main issue is how the decaying soil will often form gas that can rot plant roots if you don't poke the soil every now and then. Aside from that, as long as you have lots of plants in there from the outset, as well as plants that spread themselves rapidly, dirted tanks aren't very hard at all to maintain.

Would I recommend keeping anything more demanding than medium-low to medium light plants in them? No, but I believe it's a cheap and acceptable beginner's planted tank. It was for me!

Glad to see you had success with dirted tanks I've had more issues with it than I cared to deal with, hence I went with the aquasoil route. I've had some dirted tanks for 2-3 years now, and I was really just not satisified with the performance as compared to aquasoils. But when dirted tanks work, they really work. I used this one mix of red dirt, river silt, and some clay. That was probably my best project, but it was set up for a client in hawaii.

Great write up. I may eventually go that route some day on a smaller scale (10 gallon). My major concern is when the substrate loses its nutrients and turns to mush and needs to be swapped out. That sounds like a nightmare

I've heard of this happening, but I think the main way to combat the nutrient loss is to dose the water column with ferts so the substrate will absorb the nutrients over time. Worst case scenario (I haven't tried this yet), I can remove all the plants and fish and leave just the substrate in the tank. Then I supersaturate the substrate with an insane amount of liquid ferts to rejuvenate the substrate. Not sure if this will work, but if the substrate has a high CEC value, it may prove to be effective.

I think this is the main question people have with soil substrates. I have read conflicting information regarding this, so it is very confusing. (I am a complete beginner, and have just started a dirted tank) Theoretically, the waste for the livestock should reinvigorate the substrate just as manure will reinvigorate terrestrial substrate. Whether that works realistically I am unsure. As stated, I have read conflicting resources.

For me personally, I've never had livestock waste actually help with plant growth. I've kept dirted tanks with hundreds of guppies and a decent amount of BN plecos (100 gallon stock tank), and the plant growth was the same even without that bioload. I also fed heavily. Not much improvement I noticed, but that is just my experience.

 

For me personally, I've never had livestock waste actually help with plant growth. I've kept dirted tanks with hundreds of guppies and a decent amount of BN plecos (100 gallon stock tank), and the plant growth was the same even without that bioload. I also fed heavily. Not much improvement I noticed, but that is just my experience.

My comment was more in reference to replenishing the substrate with nutrients more-so than helping plant growth; but good to know!

To be honest, I am not sure. I have read reports that certain brands exhaust within a year, while others go strong for years on end. I think it's important to also dose the water column with ferts, because the substrates will absorb these ferts over time and retain nutrients for a longer time due to their high CEC

Great information, thank you!

 

Great write up. I may eventually go that route some day on a smaller scale (10 gallon). My major concern is when the substrate loses its nutrients and turns to mush and needs to be swapped out. That sounds like a nightmare

I don't know where the theory that aquasoils turn to mush and lose their nutrients started. The initial burst of extra ammonia will stop after a few weeks but that's it. It also doesn't turn to mush. ivehad my substrate since 2015 and its still perfectly fine.

I think this is the main question people have with soil substrates. I have read conflicting information regarding this, so it is very confusing. (I am a complete beginner, and have just started a dirted tank) Theoretically, the waste for the livestock should reinvigorate the substrate just as manure will reinvigorate terrestrial substrate. Whether that works realistically I am unsure. As stated, I have read conflicting resources.

The high cec ratio of aquasoils basically means that it will absorb ferts dosed to the water column and nutrients in the water and make them available for the roots.

Livestock Waste is your source of ammonia for your plants that's all. You can have too much or not enough.

 

I don't know where the theory that aquasoils turn to mush and lose their nutrients started. The initial burst of extra ammonia will stop after a few weeks but that's it. It also doesn't turn to mush. ivehad my substrate since 2015 and its still perfectly fine.




The high cec ratio of aquasoils basically means that it will absorb ferts dosed to the water column and nutrients in the water and make them available for the roots.

Livestock Waste is your source of ammonia for your plants that's all. You can have too much or not enough.

To be fair, I've known a few people who's aquasoil turned to mush after a while. Granted, they were using super hungry plants like some massive echinodorus, and were constantly rescaping. But I assume if you seldom rescape or maintain the substrate properly, it'll last for years.

 

To be fair, I've known a few people who's aquasoil turned to mush after a while. Granted, they were using super hungry plants like some massive echinodorus, and were constantly rescaping. But I assume if you seldom rescape or maintain the substrate properly, it'll last for years.

Even with constant rescaping is shouldnt turn to mush. Ive got 5 swords. 1 Amazon, 1 ocelot and 3 great big tank busting echinodorus uruguayensis in my tank since day 1 that have all been moved a few times

 

I am about to remove eco complete out of a 90 gal. Would it pay to use Aquasoil? And how many pounds would I need. What type of Aquasoil did you use that lasted 5yrs? Does it need to be capped off and even if not needed can I still cap it off (just not a fan of black). The eco was terrible!! I have standard gravel in a 125 and all plants grow great in it. I feed flourish ferts and osmacoat/API root tabs. Nothing to hard just easy plants. In the eco tank most of these plants done the same way will die off.
So for someone who likes plants has been growing them for 20+ yrs. will an Aquasoil impress and maybe let me grow some harder more red plants? After the waste of eco it’s tough to just jump into another that may just fail and also have to be removed in 2 yrs.

 

I am about to remove eco complete out of a 90 gal. Would it pay to use Aquasoil? And how many pounds would I need. What type of Aquasoil did you use that lasted 5yrs? Does it need to be capped off and even if not needed can I still cap it off (just not a fan of black). The eco was terrible!! I have standard gravel in a 125 and all plants grow great in it. I feed flourish ferts and osmacoat/API root tabs. Nothing to hard just easy plants. In the eco tank most of these plants done the same way will die off.
So for someone who likes plants has been growing them for 20+ yrs. will an Aquasoil impress and maybe let me grow some harder more red plants? After the waste of eco it’s tough to just jump into another that may just fail and also have to be removed in 2 yrs.

It's a good substrate, but understand it's buffering capabilities (its best used with RO water so as to not exhaust it), it's ammonia leaching (it has a break in process that involved big frequent water changes while the ammonia is released) , it's lifespan (it will exhaust and break down over time, how long depends on each and every tank).

I personally like inert plain sand or gravel plus fertilizers.

 

I am about to remove eco complete out of a 90 gal. Would it pay to use Aquasoil? And how many pounds would I need. What type of Aquasoil did you use that lasted 5yrs? Does it need to be capped off and even if not needed can I still cap it off (just not a fan of black). The eco was terrible!! I have standard gravel in a 125 and all plants grow great in it. I feed flourish ferts and osmacoat/API root tabs. Nothing to hard just easy plants. In the eco tank most of these plants done the same way will die off.
So for someone who likes plants has been growing them for 20+ yrs. will an Aquasoil impress and maybe let me grow some harder more red plants? After the waste of eco it’s tough to just jump into another that may just fail and also have to be removed in 2 yrs.

Weird. My Ecocomplete grows plants better than whatever aquasoil my Fluval Flora came with. Eco grows plants like magic for me.
I have never tried capping dirt because I fear pulling up a plant and filling the tank with dirt.