Planted tank soil substrate…


Aug 9, 2021
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Hi guys,

So I have a 200 litre tank on the way and this will be my first “big” aquarium. I currently have planted tanks that are doing really well with root tabs but I want to make sure that this big one is perfect and low maintenance. I am looking to go with a black gravel substrate and have read it would be best to underline this with some aquarium soil. My question is how does this soil work regarding maintenance? Obviously with gravel I will have to siphon it every week to clean out any debris that falls through the gaps, but I am unsure what to do with the soil? Does it ever need to be changed? If that is the case, it seems like I would have to empty the tank and uproot all the plants, remove the gravel and then remove all the soil which I assume would make the tank dirty and seems like an awful lot of effort. Is this correct or will the soil simply last forever? Thanks for any help guys!
I know there are some that feel that a 'dirt' tank has benefit, but I tend to think of it as a mucky mess. Father Time swears by pond mud covered with gravel.
I tend to favor 3-4" of sand - either pool filter or play sand. The particle size of sand is such that waste and uneaten food doesn't get down under, so the sand need never be disturbed...which makes for an excellent environment for beneficial bacteria and microbes.
Sure, an inch or two of 'dirt' may have some nutrients in the beginning, but before long it would be inert and of little value. Any subsequent moving of plants tends to be messy.
I have sand in all my tanks that remains undisturbed.
So you have to choose.
So if you were to go black gravel, would you recommend root tabs as opposed to a layer of soil?
I concur with @AbbeysDad and will add a bit more data. "Soil" can mean actual dirt, as in some form of organic potting soil or garden soil, or some of the manufactured "soils." I doubt very much the latter are actual dirt but more likely some concoction of "enriched" plant substrates. Some of these may--and it is a big may--have some nutrient benefit, but many have none. I had Flourite for two years, it was more problem than benefit, it got dumped in a hole in the back garden and I went back to inert play sand. Any of these substrates (the plant "soils" or whatever they are) have problems for substrate level fish, bacterial issues, and frequently minimal if any actual plant benefit. Inert sand can be fertilized periodically with substrate tabs, and these provide good nutrition but even more importantly do not harm fish. They also do not encourage algae.

True dirt soil has one and only one benefit, if it is a benefit. And this is the breakdown of the oprganics begins immediately, providing CO2. This is the only benefit. Ammonia is also produced, a lot of it, and most soil tank people recommend dry start and no fish for six months. After one year, the soil is completely exhausted, and has no more nutrient benefits than inert sand after the same period of time.
And to give a completely opposite viewpoint there are many good "aquasoils" available. My personal favourite is ADA. No need to bother with things like "power sand" etc but a decent aquasoil can work really well and doesn't have to be covered with another substrate. I prefer it over root tabs and inert substrate as it doesn't need to be replaced constantly and there are no pockets of low nutrient areas like you get from root tabs.

I still gravel vac but only skim the surface, no deep cleaning needed.

Will the nutrients run out from the soil? Yeah eventually. When I have run pure ada style tanks with very light water column dosing generally I start to see a drop off in plant growth after a couple of years. If I'm also dosing a heavier water column fert it can last a lot longer.

Once you do eventually start seeing plant growth drop off (which will take long time) then you don't have to uproot everything. Just treat it as an inert substrate and use a few root tabs/water column ferts.

A good quality aquasoil will absolutely work fine on its own for a good period of time (years). You can for sure go with an inert substrates with root tabs and that works too.

I have used a number of other "soil" substrates from potting soil to pond soil. They can all work but I find aquasoil to be the most straight forward and least hassle (though that comes with a price tag).

Lots of options and most of them work pretty well. Which one is best depends on personal preference.

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