I just can't stop messing with this tank's parameters. I just love tweaking my dosing and finding out how plants react!
I like to aim for less than 10ppm NO3 swings per week, and similarly I try to maintain 1-2ppm PO4 swings per week. My macros solution added 0.3ppm PO4 for every 1ppm NO3, which meant that with daily dosing, my PO4 levels were fluctuating quite a lot through the week. I recently decided to reduce my daily PO4 dosing from 0.3-0.6ppm PO4, to 0.1-0.2ppm PO4. To account for the lesser daily dose, I'm now front-loading some KH2PO4.
Separately, I've been having pale growth despite dosing 25-30ppm NO3 each week, and continuing to see some signs of trace toxicity. I was interested in how pH affects nutrient availability, because in my tank with 40-45ppm CO2 I'm consistently sitting at ~5.2pH during the photoperiod due to how acidic my water is from CO2.
Before anyone gets angry: YES I know these charts don't always track to our ionic water column scenario, but at least in soil, my macros wouldn't be very available at 5.2pH:
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I've been curious as to whether my super low pH has made it a bit more difficult for plants to get my macros, and specifically Mo as traces.
Mo is a paired nutrient with NO3 for creating green growth, so maybe all of it combines to make it difficult for plants to get all of what they need at my super low pH?
Also, my substrate has ZERO cation/anion exchange capacity, unlike aquasoil. Even 'spent' aquasoil will help plant roots "grab" nutrients from the water column, so I suspect users running zero dKH with aquasoil (or less than 40ppm CO2) wouldn't see the issues I've been having.
So I'm experimenting with raising the KH of the incoming fresh water to 3dKH via KHCO3 and NaHCO3 (baking soda).
So far so good, it appears after only a few days of raising my pH/KH via these carbonate sources that certain deficiencies are improving??
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Daily CO2 rate/min is the same, which is reflected by the similar height from max to min of all peaks (I have a ~1pH drop from the early morning to late afternoon. If it were a degassed sample, it would probably be a 1.5 drop).
Point is, same CO2 injection, but instead of happening between 6.3pH to 5.3pH every day (probably a 1.5 "pH drop", remember), it's happening at/around 6.7 to 5.7pH.
Pearling is crazy strong after raising the tank's KH from <1 to ~3. It's too soon to tell anything, but I think I'll hang here at 3KH for a few weeks and see how the plants fare.
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Things are starting to look lush!
Tank info:
New 67% WC dosing
(actual tank volume is 34 gal, I change 22.7gal aka 2/3rds, or 67% each week)
- Macros solution:
- 30mL after WC
- Front loads incoming 22.7gal water to 22.5-2.25-15, then daily 2mL dose adds 1-0.1-0.67 every day to full 34 gal tank volume each day.
- GH, KH, K, PO4 (to incoming 22.7gal):
- 10g CaSO4*2H2O (27ppm Ca),
- 7.8g MgSO4*7H2O (9ppm Mg, 3:1 ratio),
- 0.708g KH2PO4 (5.75ppm PO4 (total 8ppm), 2.38ppm K (tot. 17.38ppm K)),
- 2.78g KHCO3 (0.9dKH, 12.62ppm K (tot. 30ppm K)),
- 5.4g NaHCO3 (2.1dKH (tot. 3dKH), 17ppm Na),
- Micros solution:
- 6mL after WC
- Then 7mL/day (0.07ppm Fe, then 0.07ppm Fe daily)
- Total weekly front load:
NO3 - 22.5 ppm
PO4 - 8.0 ppm
K - 30.0 ppm
Ca - 27 ppm
Mg - 9 ppm
KH - 3.0 dKH
Na - 17 ppm
Fe - 0.07ppm
