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I'm already far in the process of making by own sand and gravel from ground from my garden or a nearby location (e.g. in order to avoid buying and transporting stuff over many kilometers that I can make myself or for aesthetic reason) (medium sand, coarse sand and fine gravel (= 0.2 to 6.3 mm) according to ISO 14688-1:2002) and already

  • made sure I'm not violating environmental or property laws when aquiring the ground
  • sieved the ground with two sieves determining the minimal and maximal size of grains[1]
  • rinsed the gravel multiple times (like I'd do for store-bought gravel)
  • desinfected the gravel with boiling water and paracite desinfection (for living food)

I assume that the small remaining amount of biological particles will be destroyed by filtering and composting during the warm-up phase of the aquarium.

The only issue I'm having is to remove the carbon/peat particles from the resulting gravel. The particles are ugly and might cause the pH value to be instable for a long time. I figured that particles could be removed

  • with an aquarium vacuum cleaner (from a bucket), but they repeatedly block the tube because peat is much lighter than the ground (but don't float all). The method allows very good separation with almost no loss of ground material and waisting of water, but is annoying.
  • by crushing it in a mortar or mixer (probably one about whose look you don't care too much about and which can be cleaned easily). The progress of smashing the peat in the mortar is inacceptably slow and an average mixer without a sharpened rotor already destroys up to half of the sieved ground which is too much loss.
  • by burning all organic material on a ceramic net on a tripod with a Bunsen burner. I didn't try that. I appears energy wasteful and expensive to buy.
  • by removing the carbon with (bio-)chemical reaction(s). Those might take long time (since peat is already quite reduced to carbon) or intoxicate the ground, so they have to be chosen carefully. I didn't figure out any.

I'm looking for the solution which is both sustainable in terms of resource consumption and not time consuming. I don't plan to produce more than 10 kg of gravel.


[1] Not determining a minimal size causes infinitely fine grained dust to block filter or remain in the aquarium for ever which causes blur at every move of a fish or hand.

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Okay, so it seems like you're saying that you've collected local gravel that you want to use in your aquarium. You're currently in the process of making it fish safe. You've already sized it and rinsed it like you would aquarium gravel. Now you have a mixture of gravel and peat and you want to separate out the peat.

The first thing that I would try is putting it in a 5 gallon bucket in batches. Don't fill more than 1/3 of the bucket with the gravel. Take a water hose and fill the bucket up. Keep the hose blasting into the bucket, agitating the gravel. Use your hand, as well, to stir the gravel up. As you noted with your aquarium vacuum, the peat is lighter than the gravel. The gravel will quickly settle to the bottom and the peat will be suspended in the water if it hasn't already flooded over the rim of the bucket. When you get it good and stirred up, tip the bucket over and dump out all the water you can without dumping the gravel out. Turn it back upright and repeat till you're no longer seeing particles floating in the bucket. Set that batch out to dry and start on another batch.

I think that will get rid of most of your peat easily. You're right, though, to worry about changing the chemistry of your water. Peat moss is acidic. That's one reason I use it for my carnivorous plants. It will make your water more acidic as it leaches into it. However, there is only so much difference it can make. If you get most of it out, the change will be very small. If you want to test it, simply take any container and fill it half full with a random sample of the gravel mix. Fill it to the top with water. Then use a pH test kit and see where it's at.

Another method you could use to help get rid of impurities that will affect your water chemistry is to put the gravel mix in a bucket, cover it with water, and let it sit for a month, dumping and changing the water every 3-4 days. This is the method you use when making concrete inserts to go in fish tanks. I saw a guy doing it when he was building a custom "rock" insert for his cichlids out of concrete. He had to leach out everything that would harm the fish. If it works with concrete, it should work with your gravel mix to reduce any agents that want to leech out. Then you wouldn't have to worry about any smaller particles that you missed. This is also the method I use to process new peat moss and sand that I use on my carnivorous plants to remove things like salts that could damage my plants.

Another reason to use that method is because you might not be sure of the type of gravel you have. Some rocks can break down and release things into the water. Limestone comes to the top of my head, but I understand other rocks can leech things into the water.

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Please note @Dalton's advices on possible problems on using gravel from earth - and give credit.

After making quite a lot of gravel myself - or more processing a lot of earth since the outcome is minimal - if figured that the separation of biomass from the gravel if the most difficult part in terms of aesthetics.

Based on a post on chemistry SE I experienced the most efficient process to separate biomass to be using the magnesium sulfate epsomite which is contained in salt fertilizers and costs about 1 € for the use case (5 € for the bag).

I dissolved approx. 1 kg of "Compo Bittersalz" fertilizer (containing 16% MgO and 13% S) into 1 l of tab water at room temperature until the solution was saturated. Then I added the gravel and mixed intensively and removed the mounting peat with a fine sieve (5 times). Then I mixed and poured the top water into another container through the same sieve (5 times). That removed about 95% of biomass remaining after sieving and intensive rinsing which is a good and quick result. The solutions can be preserved and reused.

The resulting gravel should be rinsed intensively before boiling, disinfecting and adding it to the aquarium. Mollys and shrimps do seem to like it very much.

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    another simmilar method is to use sea salt disolved in water at the same consentration as in the answer(it costs less)the rinsing is still important. – trond hansen Nov 9 '18 at 13:43

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