dKH in cycling tank fell from 6.7 to less than 0.5! - The Planted Tank Forum
 
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post #1 of 4 (permalink) Old 07-23-2014, 02:22 AM Thread Starter
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Question dKH in cycling tank fell from 6.7 to less than 0.5!

I'm setting up a new 24 gallon aquarium with Aquasoil, without another aquarium to seed the bacteria. The soil leached ammonia into the water and I've been monitoring the parameters, waiting for the ammonia to disappear. I tested the kH on the first day but haven't tested it for a few days.

On the 19th I tested the tank for leaks and tested the tap water while I was at it. The dKH was 6.7. On the 20th I put the substrate in and that evening I tested everything except dKH, thinking there wouldn't be any reason to see it drop.

I tested it today and the dKH below 0.5. This is with a Salifert test kit so it's adequately accurate. I tested it again, to make sure I didn't make a mistake, and 3 times, it tested about 0.4 or 0.5 dKH. I've added 11 grams of sodium bicarbonate (regular, not anyhydrous) to correct it back up to around 5 dKH but I've never seen carbonate hardness fall this fast.

Has anybody else seen this happen? There are no plants, no lights. Just cycling the ammonia spike... Am I going to have to test my dKH daily for a while when I introduce plants next week?

Oh and I don't have a GH test kit. I guess I should go get one :P.
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post #2 of 4 (permalink) Old 07-24-2014, 12:07 AM
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ADA products remove carbonates from the water.
This can allow the pH to drop.

This is bad for the nitrogen cycle bacteria.

While you are cycling the tank add carbonates as needed to keep the KH well above 3 degrees.

I have indeed seen it fall that fast. I was cycling a tank with Safe-T-Sorb, another substrate that removes KH.
The KH dropped from tap water normal of about 4 degrees to unmeasurable over about 2 days.
pH comes out of the tap at almost 8 because the water company adds sodium hydroxide. I suspect the Safe-T-Sorb also removes this, because the pH was below 6. Had to get a laboratory test to show it was at 5.6.

This also stalled the cycle. The bacteria quit reproducing, though they had not died.

I started adding baking soda, and kept on testing and adding as long as I was cycling it. By keeping the KH up the bacteria were able to finish growing to a nice big population.
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post #3 of 4 (permalink) Old 07-24-2014, 07:31 PM Thread Starter
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Quote:
Originally Posted by Diana View Post
ADA products remove carbonates from the water.
This can allow the pH to drop.

This is bad for the nitrogen cycle bacteria.

While you are cycling the tank add carbonates as needed to keep the KH well above 3 degrees.

I have indeed seen it fall that fast. I was cycling a tank with Safe-T-Sorb, another substrate that removes KH.
The KH dropped from tap water normal of about 4 degrees to unmeasurable over about 2 days.
pH comes out of the tap at almost 8 because the water company adds sodium hydroxide. I suspect the Safe-T-Sorb also removes this, because the pH was below 6. Had to get a laboratory test to show it was at 5.6.

This also stalled the cycle. The bacteria quit reproducing, though they had not died.

I started adding baking soda, and kept on testing and adding as long as I was cycling it. By keeping the KH up the bacteria were able to finish growing to a nice big population.
Thanks for the sharing of your experiences because I thought I was going crazy. I'm now adding 3-4tsps of baking soda, dissolved in aquarium water, once in the morning and once in the evening to keep up with it. I haven't even seen a saltwater aquarium precipitate this much carbonate!
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post #4 of 4 (permalink) Old 07-25-2014, 01:08 AM
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If you are concerned about how much sodium you are using you can also use potassium bicarbonate. I think it is sold as some sort of vitamin supplement, but I got mine from a bag sold as agricultural supply (50 lb bag, shared among friends)
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