[dwalstad]

Received following question (see below) from R. about mineralizing soil:

"I am planning a 20 gallon planted tank using soil in the future, potentially several months from now. Would it be safe to put the necessary potting soil into a bucket with water now, so that the chemical "chaos" is finished by the time I set up the tank later this year?"

The main problem I see with mineralizing soil beforehand: An organic soil put into a bucket (thick layer several inches thick), will go through prolonged anaerobic decomposition, generating copious fermentation products (e.g., acetic acid). If levels are high enough, they could inhibit plant growth when the soil is put into the tank.

In my procedure, the mineralizing is done in the tank itself. Advantages are that with the plants, water movement, and a shallow soil layer, the soil should stay relatively aerobic. The other thing is that the soil decomposition takes a couple weeks to really crank up and create chaos (my book, Fig VIII-6 on page 131). If the hobbyist has set up tank with ENOUGH good rooted plants, the plants should be able to establish themselves beforehand and counteract the increasing chaos due to bacterial decomposition. (However, so many hobbyists skimp on plants and/or use non-competitive ones. )

That said, mineralizing soil beforehand is a credible method. Our esteemed moderator Michael has set up many successful tanks with soil that he mineralized beforehand. It works well for him and others. I'll let him describe the procedure or people can search the archives here for advice on this.

 

[Michael]

There is an excellent article on mineralized topsoil in the Library forum. A big part of the mineralization process is to keep the soil in a moist, oxygen rich environment for a long time so that any organic matter can decompose rapidly and aerobically. As Diana points out, leaving a thick layer of soil submerged in a bucket longer than 24 hours is the exact opposite.

This is a good opportunity to explain how my attitudes toward mineralization have changed over the years Again, Diana is correct that you can mineralize soil in the tank. I like to do it outside the tank because I am lazy about water changes. The need to mineralize the soil increases as the organic content and fertility of the soil increase. In other words, a true natural topsoil is usually less than 5% well decomposed organic matter (humus) and has moderate fertility at most. As described, uncontaminated natural topsoil is safe to use without preparation.

Contrast natural topsoil with prepared potting mixes which may be 100% organic matter, much of it only slightly decomposed. And these "soils" are often fertilized with manure or artificial substances. This type of substrate needs good preparation, either inside the tank as Diana prefers, or outside the tank as I like to do. Highly organic fertilized soils also benefit from the addition of an inorganic, high cation exchange capacity substrate. I think of this as a way to mimic the lower organic content of natural topsoil.

The methods are slightly different but the goals are the same. Thanks, Diana!

 

[dwalstad]

Excellent insight, Michael. Makes perfect sense! Thanks for coming to my rescue.

 

[aquabillpers]

When I set up a new tank, I start with cheap topsoil from a big box store and soak it it a 5 gallon bucket. Periodically I stir the bucket. I do that to get rid of wood and other stuff, but now I see that I am also preventing the problens that Diana described.

BTW, the term "mineralize" always seems a little clumsy to me. How about using "deorganicate" instrad?

Well, maybe not.

Bill

 

[Karen in San Jose]

I'm just setting up my first Walstad method tank and I've never had a tank with plants that lived - just to give you a sense of who you're dealing with here. But, I'm retired and very curious and a research-freak. My copy of Diana's book has tabs sticking out all over it. I'm determined to eventually figure this all out. For the record, I have bred corydoras and had lots of tanks in the past, but just with gravel and fake plants.

I'm wondering if putting blackworms in the tank will help speed this process along. They eat decaying stuff in soil like leaves and wood, etc. I used to feed them to my corys and I ended up with a bunch of them living in the gravel in the tank and they never caused any problems as far as water quality, etc.

So, for experimental fun, I ordered some blackworms and I'm going to go ahead and put a bunch of them in my tank. I intend to get fish that will love having them in there, once the tank gets settled. I don't mind seeing their tails sticking up like grass in the substrate. I think they're cool creatures.

Has anyone else tried this that you know of?

 

[mistergreen]

I'm just setting up my first Walstad method tank and I've never had a tank with plants that lived - just to give you a sense of who you're dealing with here. But, I'm retired and very curious and a research-freak. My copy of Diana's book has tabs sticking out all over it. I'm determined to eventually figure this all out. For the record, I have bred corydoras and had lots of tanks in the past, but just with gravel and fake plants.

I'm wondering if putting blackworms in the tank will help speed this process along. They eat decaying stuff in soil like leaves and wood, etc. I used to feed them to my corys and I ended up with a bunch of them living in the gravel in the tank and they never caused any problems as far as water quality, etc.

So, for experimental fun, I ordered some blackworms and I'm going to go ahead and put a bunch of them in my tank. I intend to get fish that will love having them in there, once the tank gets settled. I don't mind seeing their tails sticking up like grass in the substrate. I think they're cool creatures.

Has anyone else tried this that you know of?

I've seen it done but not in a dirt tank. You might find dirt moved above the cap substrate through their activities.

 

[Karen in San Jose]

I've seen it done but not in a dirt tank. You might find dirt moved above the cap substrate through their activities.

Ah, good point, thank you. Hmmmm. Well, I think I'll give it a go and see what happens. I'll let you all know. The grand worm experiment.

 

[Michael]

I think Diana has experience with blackworms in a soil substrate tank.

 

[dwalstad]

Blackworms are great! They aerate the soil and your fish will love them.

 

[Karen in San Jose]

Thank you so much for the replies! I got a message from the blackworm seller that her fridge died and her blackworms all turned to mush. What a bummer for her! I'm actually rethinking getting corys now, because I am learning what a pain it is when the soil gets disturbed and floats up to the surface lol. I'm thinking I don't want anybody digging for worms after all. I may change my mind at some point, but for now the great blackworm experiment is on hold.

I really wish I'd read Diana's paper on small shrimp tanks earlier, in particular for the sentence included about why she uses the soil she does, specifically the part about how annoying it is for the perlite pieces to come floating out of the substrate.... at least they're easy to remove

 

[dwalstad]

I wouldn't veto any potting soil because of perlite. A minor nuisance that can be easily remedied--as you have alluded to. Perlite is a natural product. Focus your attention on things that matter--plants (number of easy-growing species), substrate depth, and water hardness.

Don't discount blackworms. Corys love them. You may not be able to maintain a colony, because the Corys will pick them off. However, the fun of tanks is the tinkering and playing around.

 

[Karen in San Jose]

I wouldn't veto any potting soil because of perlite. A minor nuisance that can be easily remedied--as you have alluded to. Perlite is a natural product. Focus your attention on things that matter--plants (number of easy-growing species), substrate depth, and water hardness.

Don't discount blackworms. Corys love them. You may not be able to maintain a colony, because the Corys will pick them off. However, the fun of tanks is the tinkering and playing around.

Thanks so much for the advice. I really appreciate it.