Feed your DIRT

First let me nearly disqualify myself as I do not have a dirt tank. My 60g is a somewhat sterile canvas with a gravel/sand substrate and (dare I say it) plastic plants (although I do have real rocks!).

I have however been involved in organic gardening for over 30 years. In so doing, I have made tons of compost and have even made truckloads of vermicompost (composting with redworms).

In order to produce healthy plants, fruits and vegetables, you have to FEED THE SOIL. There is an incredible ecology that happens in the soil in order to breakdown organic matter into plant usable nutrients.

So your starting out with nutrient rich organic potting soil, perhaps augmented by some clay and/or other additives. After a bunch of water changes and filtration and a bunch of plants, things are looking good. Assuming decent lighting and water quality, the plants should be growing really well...but unless you take measures, things will level off and in time, plants will not grow so well. Now here's where some will be tempted to start using petro-chemical fertilizers in liquid or root tab forms. Well, if you were gonna end up doint that, you might as well not started with dirt at all - just used sand/gravel and done hydroponics!

If you have a dirt tank, you need to FEED THE SOIL and develop the ecosystem. In so doing, we'll borrow a couple of ideas from the 'deep sand bed' folks.

First, your soil needs a constant supply of organic matter so to decay and feed your soil. So put that gravel siphon down and leave the mulm alone. A layer of decaying mulm is essential in maintaining the health of your aquatic soil. If you want a cleaner look, say in front, slosh the mulm towards the more heavily planted rear of the tank rather than removing it. Of course you can do some cleanup, but try to keep as much organic waste as possible that will feed your subsoil...and ultimately feed your plants.

If you don't have sufficient stock, you still need to find a way to organically enrich the soil - perhaps by adding fish food for invisible fish ;-)

Consider adding some subsoil life. California black worms are the aquatic equivalent to redworms. They will burrow and aerate the soil, process decaying organic matter and their castings are pure organic gold in the substrate.They will also make a most excellent supplemental food source for your fish.

Malaysian Trumpet Snails will burrow in the top inch of gravel/sand keeping it aerated. This assists the bacteria that lives there and breaks down organic matter further.

I could go on and on here, but don't want to 'preach to the choir' or wear out my welcome. I'm very interested in the soil substrate aquarium and will start one when I have the space and time. I wrote this because I've learned alot about good growing soils and what I've seen so far regarding the 'dirt tank' doesn't seem to address long term organic maintenance of the subsoil, so I thought I'd toss this out as food for thought.

If you got this far, thanks for reading - hope you saw some value in it.

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Permalink Reply by 2apes2gp667wr on December 4, 2011 at 2:06pm

Fear of anaerobic bacteria releasing tons of hydrogen sulfide is some sort of weird self imposed scare tactic. 1% of people have it happen at a dangerous level but everyone fears it like it WILL happen & WILL kill your whole tank.

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Permalink Reply by Michael V on December 6, 2011 at 10:32am

Actually is pretty real if you create too deep a bed with organic potting soil. The problem is there is enough raw organic material in potting soil that's not fully decomposed. If the substrate is too deep, anaerobic bacteria will go to work to break it down...and nasty gases can result. If your just growing plants, the gases will bubble up w/o much of an issue. With fish, it may be a disaster!

It is much better in deeper beds to use plain old top soil or mineralized top soil rather than potting soil. So the recipe would be 2" of top soil (or MTS), 1" of organic potting soil and 1"+ of sand to cap. (just my $.02).

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Permalink Reply by 2apes2gp667wr on December 6, 2011 at 1:30pm

I have no doubt it could happen. I've just never heard one first hand account of a tank getting gassed and all the livestock dying. Unless someone just did a set it and forget it.

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Permalink Reply by Josh C. on December 12, 2011 at 4:03am

Would adding a layer of organic compost (i.e fruits, vegetables, leaves, ect...) to dirted tanks benefit plants?

In theory, as the organic matter breaks down it would charge the dirt with nutrients and bacteria feeding the plants and promoting lush growth.

Any thoughts on this would be greatly appreciated.

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Permalink Reply by Sin the conqueror on December 12, 2011 at 4:10am

green compost or uncomposted fruits, vegetables, and junk are very unstable and might harm your aquarium with different gasses and toxins that they give off while going through decay. a few decaying leaves is nothing compared to how much junk a rotting apple gives off.

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Permalink Reply by Jarrett Hunt on December 12, 2011 at 4:24am

When you say compost are you talking pre decomposed or putying fresh fruit under soil. I would just make my own compost with fruits, vegetables, leaves, ect to make sure that gases are gone by the time you put it in the tank. At least you'll know what's in the compost.

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Permalink Reply by Josh C. on December 12, 2011 at 4:29am

yes that's what i meant. this was just a random idea i had today. Im not very familiar with how to make compost, other than the basics.

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Permalink Reply by Jarrett Hunt on December 12, 2011 at 5:25am

It shouldn't be too hard to make it. I know "Espoma" makes and sells a compost starter to help get the break down going.

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Permalink Reply by Michael V on December 12, 2011 at 2:05pm

First, lets be very clear that we do not want excess organic matter (even compost) deep in the substrate as this tempts fate. The lower substrate (1-2") should be plaint old top soil or mineralized top soil. Then we add a layer of aged compost or vermicompost (compost made by redworms).

To make compost, you need greens (nitrogen), browns (carbon) and water. I like to use grass clippings and dry leaves, layered in a pile (grass, leaves, grass...) with ample moisture. Within no time, the pile will heat up to temps 120F-140F. As the temp falls off, the pile needs to be turned, with more moisture added. This repeats until the pile will no longer heat and you're left with "black gold".

This time of year, it may be easiest to just buy compost or composted cow manure from the local ag or big box store.

Remember, we'd only want a thin layer )1/2" or so) between the top soil substrate and the sand/gravel cap.

Most of the food you'll feed your soil with will be fish food, fish and plant waste by letting the mulm decompose naturally on top and in the very upper layers of the substrate. This process is further augmented by malaysian trumpet snails and California black worms - assuming you're shooting for a true self sustaining biotope...and why not since with dirt and plants your so very close!

If you do the above, you should need little if any fertilizer additives. I would let the plants 'tell' you if they need additional fertilizer to remain healthy. Bear in mind that you may or may not be looking for maximum growth requiring pruning, but maximum health in color and overall appearance.

Also: be advised that a layer of compost will likely produce 'compost tea' which may result is an additional water change or two~.

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Permalink Reply by Sin the conqueror on December 12, 2011 at 3:05pm

+1 michael.

where do u guys get your black worms? i got it at my LFS but mines a fish store on crack and THEY ARE GREAT!!! ive traveled all around the US in the past 4 years for work and ive never seen a store with worms