Originally Posted by JDM
Hmmm, then what I s going on in my tank I wonder... I'm going to test tonight or tomorrow out of curiosity. On the 26th it was at. 21dGH and 16dKH.
21st post 75% WC = 21dGH and 16dKH
22nd post 30% WC = 19dGH and 17dKH
25th no WC = 21dGH and 16dKH
26th added 9 catfish, 4 red hygrophila stems , 1/2 a tank surface of duckweed
31st no WC = 21dGH and 16dKH
Difference in the tank since the 26th would be an increase in ammonia concentration, measurable as "non-zero" so not near 0.25ppm except once.
Not a scientific result due to the non-static conditions but interesting that the hardness has not changed since the addition of the new ammonia source. I thought that the 25th result might have been false as I did not do the test myself, my daughter did, perhaps she miss counted as I wouldn't expect the GH to go up while the KH went down. Today's test confirms that the 25th test may have been correct.
Don't think I am going to get anything to explain it so I'll just chalk it up to just one more equilibrium to watch even though I don't know what the other side is.
Oh, here are some pics of the plant growth over the period.
1 = 20th
2 = 28th
3 = 30th
Seems to be a growth spurt in the last few days since the fish have been added.