# Substrate planning for new tank - capping soil with gravel & sand



## notabob (Jul 12, 2017)

I'm in the planning stages of upgrading from my trusty old 30G to a Marineland 58G. The 30 has had a basic gravel substrate for all of its 18 years. I only recently started planting it, and it's been doing ok, but gravel has proved to be less than ideal for some of the rooted plants. For the replacement tank I'm moving to black sand to make it easier on the loaches and corys as well as to improve the contrast for plants and fish, but also would really like to take advantage of the benefits that soil can offer for the plants. From what I gathered from Mr. Google so far, simply capping soil with sand may be problematic, as soil may end up rising through it, so I'm considering a thin layer of gravel in between as a barrier. So, the current substrate plan is:

- 1" of MiracleGro Organic potting mix
- 0.5" of Fluval Flourite black gravel
- 1.5-2" of Tahitian Moon black sand

So - would half an inch of gravel be enough of a cap to keep the soil put or should I plan for more? Has anyone else tried a similar combination? Has it worked well for you?

I also would like this to be a fairly long-term substrate solution that won't need to be ripped up/re-done in a couple of years. Thanks in advance for any pointers/suggestions/feedback!


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## geisterwald (Jul 18, 2016)

Sand is smaller and denser than gravel, ergo it is going to sink into the gravel over time, no matter what you do.


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## slipfinger (Jun 8, 2016)

Are you planning to uproot plants often?

One of my tanks is soil capped with PFS and let me tell you it can get really messy. No matter how gentle you are the soil will make its way out of the cap. Nothing new here, I'm sure everyone fights with this issue.

Lots of success stories with straight PFS and BDBS as your substrate. Both are cheap and clean! 

Just throwing it out there.


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## geisterwald (Jul 18, 2016)

slipfinger said:


> Are you planning to uproot plants often?
> 
> One of my tanks is soil capped with PFS and let me tell you it can get really messy. No matter how gentle you are the soil will make its way out of the cap. Nothing new here, I'm sure everyone fights with this issue.
> 
> ...


My previous tank was a MGOPS-like soil capped with PFS... not only was it a huge mess from the moment I set the tank up (and made my TDS REALLY high, no amount of substrate vacuuming could save me), it went anaerobic and killed a bunch of my livestock--or just the usual CO2 bubbles from decomposition did; I never had any smell or color in the bubbles which I had always heard was the ultimate sign of anaerobic dirt, so I was in denial for a long time about that possibility, but it stank really bad when I ultimately tore the tank down.

People say you have to poke the substrate a lot to keep it from turning; what they don't tell you is that poking the substrate itself causes a huge mess when it inevitably ruptures the dirt layer, or that your idea of "a lot" may not be nearly enough to suffice.

It seems like for every success story, there's a disaster, and there's very little telling which you'll be, no matter how prepared you think you are. I held my tongue in my first comment because I didn't want to be overly negative, but IMO it's seriously not worth it.

Like slipfinger said, there's plenty of success stories in PFS or BDBS alone--and even in gravel. With the right light and fertilizers (and sometimes CO2) you can grow great plants without putting dirt anywhere near your tank.


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## notabob (Jul 12, 2017)

Thanks! Very interesting information. If I stick to just sand, what should be the ideal thickness? Should I aim for ~3" to maximize available depth for root systems? Or would 2" be sufficient?


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## ChrisX (May 28, 2017)

notabob said:


> Thanks! Very interesting information. If I stick to just sand, what should be the ideal thickness? Should I aim for ~3" to maximize available depth for root systems? Or would 2" be sufficient?


I have a very positive experience with soil under pool filter sand. An inch of sand on top of an inch of soil. I think many problems with soil come from too thin a cap.

Any soil that comes up when replanting can be vacuumed up. Carefully filter the soil of any large particles/wood. If these come up, they can't easily be vacuumed.


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## bmillerind07 (Aug 19, 2016)

Just swapped my substrate to BDBS and I love it so far. It looks good and plants stay put for the most part.


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## reddhawkk (Dec 28, 2011)

MTS also help with CO2 pockets.


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## notabob (Jul 12, 2017)

bmillerind07 said:


> Just swapped my substrate to BDBS and I love it so far. It looks good and plants stay put for the most part.


That tank looks good. I've been having a lot of issues with my S.Repens propagation clippings not staying put in the gravel in the current tank, which was another reason for moving to sand, in addition to it being a better substrate for the bottom dwelling fish. So I'm pretty determined to go with sand as the top layer, with ~100lbs of sand sitting in the basement and waiting for the new tank to prove it . It's what (if anything) will go under the sand that I'm still undecided on.

It certainly seems like the dirt vs. no dirt debate is livelier than I thought. I'm all for keeping things simple, but a 1-time introduction of soil doesn't really bother me that much. That said, if it's going to turn into an endless battle to keep the dirt under the cap or if I'll have to rip everything up to keep the dirt from poisoning my tank in 2-3 years time - that's a different matter.

On that note, if dirt is used under a cap, is it recommended that it be removed/replaced after a time?

Apologize for what may be fairly basic questions to some - I'm still learning here...


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## BrandiB81 (Jul 31, 2017)

What is BDBS sorry I'm new and don't know all the abbreviations


bmillerind07 said:


> Just swapped my substrate to BDBS and I love it so far. It looks good and plants stay put for the most part.


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## vjelson (Jul 31, 2017)

I agree, all the posts should refrain from the abbreviations for us newbies, but I do know it's "Black Diamond Blasting Sand" because that is what I am using with a cheap sifted garden soil and clay mix substrate capped by the black sand


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## roadmaster (Nov 5, 2009)

BDBS is abbreviation for Black Diamond blasting media which is often sold at Tractor supply stores.
As mentioned,,most issues with soil leaching up through a sand cap is due to cap not being deep enough and or plant's being uprooted /moved frequently which don't do nothing for the plant's from growth stand point.
Ideally,we research the plant's first which gives us an idea on what plant's may do best in our tanks, and how they might grow with respect to height along with whether they are best suited for lower light intensity, low tech non CO2, or higher lighting,high tech CO2 injection.
I would not be afraid of two inches of soil and perhaps two or three inches of a cap be it sand or fine gravel.
Soil issues largely result of poor oxygen level's which are hard to realize in properly cared for tank's.
Soil is not for those who can't/won't leave plant's be, and most soils are good for a year or two before either need replacing,or water column dosing with nutrient's.
Can use clay,peat,mixed with the soil and maybe get another year before you start noticing plant growth not like it was when soil was newer.
Plant's been growing in dirt for eon's.


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