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Using garden clay as a substrate
- Thread starter castle
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simon_the_plant_nerd
Member
Depends on the definition of useful. Clay based soils have a much greater cation exchange capacity than a sandy soil (like an aqua soil). Though without significantly processing the clay before it’s suitable in other respects (i.e. not a massive lump which you can plant into) it may still be fairly useless.
Maybe make some pots?
ElleDee
Member
I don't think you should ever plant in straight clay from outside, though it might be a useful component in a substrate assuming it's free from contaminants.
The only thing that makes clay clay is that the rock particles are super, super tiny. So tiny that they can form a colloidal suspension if mixed into the water column and make muddy water that literally never settles out, and so tiny that they fit together very closely in the substrate and greatly inhibit root and water movement - both situations are very bad. But clays do have stuff to offer depending on what they are made from - they can have decent to very high CEC values, and they can contribute nutrients. I have used small amounts of my iron oxide-rich native clay at the very bottom of my substrate and my well rooted plants have never had iron deficiencies at times with other plants were suffering. The trick is knowing about your specific clay and then using with other components to avoid the downsides of clay. Easier said than done maybe, but hey - garden clay is free.
The only thing that makes clay clay is that the rock particles are super, super tiny. So tiny that they can form a colloidal suspension if mixed into the water column and make muddy water that literally never settles out, and so tiny that they fit together very closely in the substrate and greatly inhibit root and water movement - both situations are very bad. But clays do have stuff to offer depending on what they are made from - they can have decent to very high CEC values, and they can contribute nutrients. I have used small amounts of my iron oxide-rich native clay at the very bottom of my substrate and my well rooted plants have never had iron deficiencies at times with other plants were suffering. The trick is knowing about your specific clay and then using with other components to avoid the downsides of clay. Easier said than done maybe, but hey - garden clay is free.
I have used clay a few times with good results, both below a sand layer and on its own. When exposed it might cloud the water initially, but the particles will settle out once you get some algae on them to hold it all together. I think a doing a dry start for a few weeks until a biofilm develops could reduce the cloudiness substantially.
Plants didn't seem to mind having their roots in "pure" clay (the Utricularia gramminifolia enjoyed it very much actually), but the clay here is probably quite nutrient poor, so wont create many noxious substances (like hydrogen sulfide) while submerged. You definitely don't want to combine clay with a substrate rich in organics, that would send the redox potential down to levels where you get toxins forming. Most aquatic plants other than epi/litophytes should be used to growing in clay or similar in the wild, and should have ways to handle it provided all other parameters are good.
Plants didn't seem to mind having their roots in "pure" clay (the Utricularia gramminifolia enjoyed it very much actually), but the clay here is probably quite nutrient poor, so wont create many noxious substances (like hydrogen sulfide) while submerged. You definitely don't want to combine clay with a substrate rich in organics, that would send the redox potential down to levels where you get toxins forming. Most aquatic plants other than epi/litophytes should be used to growing in clay or similar in the wild, and should have ways to handle it provided all other parameters are good.
