Phil I highly doubt it's an Mg deficiency.
Raising RO water to dKH to about 5 with Ca : Mg at somewhere around 20 : 10 is more than enough for any tank.
So your current NO3 : PO4 : K is about 15 : 3 : 17. I am assuming when you say target you are dosing the new 30 gallons to that target? Does that K included the K from Alkaline Buffer? If not your K may be very high in relation to everything else.
Is the .1 micros dose a single dose after water change? Or daily? I ask because lack of Fe can cause pale new growth. And what micros are you using?
I doubt going from two large water changes to three would make any difference. Two changes of 85% is more than enough for any tank. But with those large changes you might need higher dosing to keep levels stable. If it were me, I would try upping just PO4 a bit for a few weeks an see what happens.
All in all it seems like you are not far off so I would not be making any drastic changes. And keep in mind when you raise light levels, there is usually an adjustment period. Every time I have done it I get an immediate slight increase in algae until the plants adjust.
I've calculated concentrations based on 35 gallons of water except for Alkaline Buffer, which is added for the new 30 gallons only. The only sources of K are Flourish Nitrogen, Phosphorus, and Potassium.
Iron and Traces are dosed independently using Flourish Iron and Trace with both doses calculated for 35 gallons. I was dosing 0.1 mg/L Fe every day at first, then every other day, as GSA was starting to be a problem. PO4 was 2.5 mg/L at the time and lights were at 10% so my supposition was too much Fe, which is why I went to only dosing at the twice-weekly water change. That being said, it could very well be lack of Fe and I won't rule that out.
I'm 100% with you; those macro, Ca, and Mg concentrations should be more than enough, but I'm seeing what I'm seeing and it's been a looooooong time since I've used an inert substrate. My first assumption since it's fairly new Flourite and I washed the daylights out of it, is there's no nutrient input from the substrate yet that might add the extra oomph we get from the active varieties.
Growth is good; noticeably so in a couple of species even during the week, which lends credence to your thought about macros. In the short term I want to give the tank a heavy blast of macros and majors to see if that does anything. There's usually a noticeable difference when I come in on Monday so we'll see what there is to be seen next week. That's one of the best things about this being in my office, a couple days without seeing the tank really helps to notice differences.
As for the 3x weekly water changes, thankfully I've got access to unlimited RO/DI and doing a simple drain-and-fill is easily done when doing the morning emails. The reason I'm doing such large and frequent changes is an attempt to run the tank with no accumulation between doses in hopes of getting a more clear picture of how the dosing's actually working. Going to a 3x weekly change and dose schedule isn't a problem and
may be worth a try in the future. Like you said, it's nice to get paid to experiment.
TLDR
Lighting got increased from 10% to 15% two weeks ago and total growth is still good. The P. stellata alone has grown almost three inches since Monday's picture.
My PAR meter needs a new battery so I have no idea what it actually is; I'm just going on how the tank responds to illumination. I'll get the meter up and running one of these days and get actual values.
CO2's as high as I can get it without killing the fish. The last time I checked it via a CHEMetrics dissolved CO2 kit was when the fish were gasping at a 52 mg/L CO2 concentration. Needless to say it got turned down a tad.
GSA is only on the older/lower leaves and the new stuff's totally clear of all algae. I've promised myself I'm not going to trim the stems until they reach the surface so make sure I give the tank time to establish and not be in a constant state of flux due to large losses of biomass. Thankfully things are nice and clean so I'm not going crazy wanting to remove algae. No, I'm not dosing Excel.
Some of the older growth is getting holes, but not the same way that K deficiency usually shows up as.
The H. siamensis and A. frazeri are showing interveinal chlorosis, so Mg is getting upped. Ca was increased slightly as well to get a roughly 1:1 ratio.
L. repens "Red", B. caroliniana, S. subdulata, and P. stellata are on the pale side. This could very well be due to a lack of Fe.
All dosing except for Alkaline Buffer is based on 35 gallons actual water volume. AB is added only for the 30 gallons replaced.
PO4 was increased to slightly over 3.0 mg/L to achieve a roughly 3.4:1.0 N : P ratio.
Fe and Trace are being dosed independently according to the standard instructions on the bottle at the moment. It'll be very easy to increase dosing on these if signs point to it.
Macros are going to be blasted for a week to see what changes show up. If things stay the same then it's very likely an Fe issue and dosing will be changed to 3x/week.
3x 85% water changes per week takes less time away from my tasks than going to the lab to test the water so moving to that regimen is a possibility in the future.
Yes, I work for Seachem so I'm expected to be using our products in this tank. Thankfully I get them all for free so I can dose as much as I want without breaking the bank.
There we have it. I think I responded to each point.
We'll see how things go between now and Monday.
Thank you for your thoughts Gregg, I appreciate them.
Thanks for watching!
Phil
