# Glacial silt as base fertilizer?



## FishWorks Alaska (Apr 3, 2016)

Greetings from Alaska, I had some glacial silt tested and found that it had...
Ph-8.42
Phosphorus-<1 ppm
Potassium-59 
Calcium-2214 
Magnesium-118
Sodium-42
Copper-13
Zinc-13
Manganese-133
Iron-795
With little or no organics
My question is, would it be a good base layer substrate? I was planning on one inch of silt and two inches of Eco complete on top. 
This is a 265 gallon set up so ADA is out of the question


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## Diana K (Dec 20, 2007)

Well, here is the question:
When you put this in the water, how much of these minerals come out of the material and enter the water? How fast?

If the material dissolves easily, then it is more of a fertilizer, and you should not use very much. Try it: Put some in water and test the water after a few hours, the next day, and a few days later. 
If the material dissolves slowly, then it might make a reasonable substrate if you treat it like limestone sand. Again, leave that sample in some water and see what happens. How fast do the minerals enter the water? Do they reach a point where they level off? Is this at a low enough point that it is safe for the fish, plants etc.? Run the test for a couple of weeks. 

Make these tests using water the way you will prepare it for the tank. Especially, if you will be using driftwood or peat moss or other acid reacting things in the tank or filter, use these in the tests. 

If the tests seem to show that the material does not dissolve, there still may be very small traces of minerals in the water that might help out as fertilizers, so be careful when you fertilize the plants so as not to create toxic levels of something.

Of this material does not dissolve in water, it might be so fine that it stays suspended in water, and could cause clouding problems. If this is so, then it may still be workable with a cap. Before setting up a really big tank, though, you might try a 10-20 gallon tank with the same proportions of substrates, and see what happens. How fast does it settle when you first set it up? What happens if you transplant and stir up the glacial silt?


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## FishWorks Alaska (Apr 3, 2016)

Thank you so much, some great ideas! I'm not sure how I will be able to test for some of them. 
I will keep up on my progress


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## JuliaAdkins (Apr 23, 2012)

While the potassium looks good both the calcium and magnesium are very high as are the micros. This could be a lovely supplement but I wonder about one third of your substrate being basically micros.


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## FishWorks Alaska (Apr 3, 2016)

As long as they don't over leach the micros, would that be a bad thing?


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## Diana K (Dec 20, 2007)

Run these tests:

1) Place the silt in a straight sided jar, such as a canning jar. Put a piece of masking tape or other tape you can write on vertically on the side. Fill about 2/3 with silt. Mark where this is on the tape. Add water (any water) to fill the jar, and a few grains or a drop or two of dish washer detergent/soap. (The stuff for a dish washer has less bubbles or foam. This is optional- if you do not have any don't go buy it just for this test) Shake really well, then shake some more. If the glacial silt is dry when you start you may have to add more water. 
Set the jar down and time it:
At 30 seconds mark how much has settled out. 
At 2 minutes mark how much has settled out. 
At 2 hours mark how much has settled out. 
At 24 hours mark how much has settled out, and how cloudy the water is. 
Convert these levels to percentages. 

Interpretting test 1:
Sand sized particles settle out in 30 seconds. Should be a lot of sand. Over 50%
Silt sized particles settle out in 2 minutes. Should be a fair amount of silt. 20-30% is good.
Clay sized particles settle out over several hours. The coarser ones in 2 hours. Most (99%) of the glacial silt ought to have settled out in 2 hours. 
If the water is still murky after 2 hours then there are finer clays. This may become a problem in the tank, because these can get stirred up every time you move a plant, or if you have fish that dig. These particles may get bound together by microorganisms, but if there is still a lot of material in the water after 2 hours I would not use this in an aquarium. 
If there is still cloudy water after 24 hours, forget it. There is colloidal clay- particles that are so fine Brownian motion keeps them suspended. This is not a good material to use as a substrate. 

2) Make some water the way you will be making it for the aquarium. Whatever additives you will be using, do that. Test this water with all the aquarium tests you have. Set up a jar with just this water. 
Then set up a jar with a few inches of substrate and a few inches of water. You could swirl it around a bit, but no need to shake it. When the water clears (hopefully in under 2 hours) test the water with all the aquarium tests you have. 
By keeping one jar with just the aquarium water, and another jar with glacial silt and the same kind of water you will know which test changes are inherent in the water, and which ones are happening because of the glacial silt. 
At the very least, I would test:
Ammonia, nitrite, nitrate, GH, KH, pH, Iron, Phosphate, Calcium and TDS. If you have any other tests use them.
Test in a few hours, the next day, several days later, then once or twice a week for 2 weeks. 
See if there is a trend in any of the tests. 

Interpretting test 2:
If ammonia, nitrite or nitrate show up, this might be temporary, run this test a bit differently (see 3)
If GH, KH, pH, TDS rise slowly, not getting very high, you may be OK with this as a substrate. Substrate that contributes very low levels of minerals to the water can be good. If these values rise too fast or get too high this material may work for hard water fish, which thrive in high GH, KH, pH, TDS, but not soft water fish. 
If the other things rise, but very little, then this may be OK. If they rise too much, then this is more of a fertilizer sort of product, and should not be used as substrate. 

Test 3:
Set up a tank and run it with the glacial silt as part of the substrate. 
Most conservative: Dust a little on the floor of the tank, then cover it with other substrate like sand. 
A bit more adventurous (if the tests in part 2 seem to say it is OK) blend the glacial silt with sand, or put a deeper layer (1/2" perhaps) in the tank, then cap it with sand. 
Most adventurous: Use pure glacial silt as substrate. 
Run the tank for a month, doing the fishless cycle, and testing all the things from test 2 about once a week. Then add fish.


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