The Planted Tank Forum - View Single Post - Using Oil-Dri for cheap substrate?
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post #30 of (permalink) Old 09-08-2012, 03:59 PM
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Join Date: Jan 2010
Location: Contra Costa CA
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Roy, I have done this before with Soil Master Select. The first time was in a 29 gallon tank, KH and pH bottom of the test (KH=0, pH =6 or lower).
Add 1 teaspoon baking soda, let it circulate. Test. KH =2 German degrees of hardness, pH = 6.2. Repeated several times on 2 tanks the same size, then later similar results with other tanks ranging from 10 gallons to 125 gallons.

So... 1 teaspoon in a 29 (Done over several years, many tanks) = 2 degrees
so... 2 tablespoons in a 88 (The tank under discussion today) = 4 degrees

There are 3 teaspoons in a tablespoon, so I added 6 times as much to a tank that is 3 times as large, so the KH change ought to be twice as much.

It was late yesterday when I added the baking soda, so I did not go check it after it had circulated, and by now the substrate has probably removed it. I will post the test results later, and what I do about it.

I also have pH test strips that came from a lab, and test lower than the aquarium tests, so I will use those. They are probably more accurate, too.
KH test is API and Jungle test strips. I can use double the water sample in the API test to fine tune the numbers. No, the tests are not calibrated. While I am willing to pretend that I have results down into decimal places, I know it is not that accurate.

I am looking at the big picture:
This substrate removes pretty much all the carbonates from the water.
This allows the pH to drop way too low for the nitrifying bacteria to reproduce. (I am running the fishless cycle on this tank, remember)
So I want to fix it.
This would mean raising the KH to at least 3 degrees, and probably higher. (The original work identifying the correct species of nitrifying bacteria used a KH of about 8-9 German degrees of hardness, if I remember).

starquest, I think that is a good idea. These products have a high cationic exchange capacity, and will indeed soak up a lot of fertilizer. When I was using Soil Master Select and the EI method of fertilizing I think I got that substrate really well saturated with fertilizers. When I stopped dosing the tanks for a while the plants continued to do well for a couple of months. I would be leery of using too much fertilizer, though. You would not want so much that it would leach out into the tank water. I understand what a dry start is, but the root zone is wet, and too much fertilizer in the root zone may not be good. So, soak the substrate in fertilizer rich water, then drain away that water and refill with ordinary water (RO, tap or whatever- not enriched with fertilizer).

On the schedule for today: Water change. The ammonia removing bacteria are growing like crazy and have spiked the NO2 too high. I am not sure about the NO2 removing bacteria. It is too soon for them to really be growing that well, but the NO3 is high, too. I am thinking some of the NO3 reading is from fertilizer, and some from the bacteria.
I will test tap and tank before and after. (Garden plants are going to love this water!)

Water company adds sodium hydroxide to raise the pH. I suppose that is another item removed by the substrate, or else why would the pH drop so much? Normally the tap water is KH 4-5 degrees and pH high 7s, occasionally low 8s.
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