Lighting & CO2 Upgrade - Mediocre Results on A. Reineckii and others
This sounds crazy, but I ran a 155-gallon aquarium with DIY CO2 for five years with pretty good results. I grew swords, vals, crypts, cabomba, ludwigia stem plants like crazy and would routinely sell $30-$50 of clippings at a time. Lighting was 4x96W PC, single T8 and dual T5 NO, with fluorite substrate. I had trouble growing A. Reineckii and Rotala Wallichii and Ammania Gracillis would have a red top but lose lower leaves, but otherwise the tank did great, even at 84 degrees for discus.
This year, I invested in pressurized CO2 and the BML Dutch XB LED to replace the PC fixtures. LED is raised 3" off top of tank, and I run it about 80% strength. The pH drop is 1.4 using the de-gas method, and I've tested that 2-3 different times, always getting about 1.2-1.4 difference. I run CO2 through two PVC reactors on canister filter returns. Pearling is great, and plants look good under the light, but growth rate isn't that much different (swords and narrow leaf ludwigia are actually slower and crypts aren't getting as big as they used to). Alternanthera Reineckii still looks terrible-I get maybe an inch of growth in 2-3 months, and lower leaves are yellowing, ratty, and have a little spot algae on them. I got Ludwigia Glandulosa a month ago, and it's transitioned to submerged growth with a nice red top, but it has lost a lot of the lower leaves. CO2 mist is directed onto both of these plants.
Ferts - with DIY CO2 and PC lights, I probably did about 1/2 EI, and based on API test kits maintained NO3 about 20ppm, PO4 at 1-2ppm, and added K and traces to the point I never saw holes in leaves, stunted tips or pale leaves. With new lighting and CO2, I have tried full EI, half EI (since tank is moderately planted) and modified EI (holding back on KNO3 since test kit shows 40+ppm and just dosing K2SO4, 20ppm per week). I maintain 50% weekly water changes. At 5-6 days after water change, tank looks generally worse than it does 2 days after W/C, with more GDA, some fuzz algae on hardscape, etc. I usually notice this right after full CSM+B dosing. Algae situation has improved recently as I have cleaned filters more often and removed mulm and dead leaves more often.
I read with interest some posts by Kekon and Defdac, suggesting that high NO3 combined with soft, low-KH water could drive plants too fast, notably A Reineckii and result in stunting similar to calcium deficiency. My GH is 7 and KH is 4 (I raise it from tap, where it is at 2). I could never get nitrate down that low (5-10), and in trying to do so I noticed ludwigia lower leaves looking bad and the plants not growing much. Plus Tom Barr grows these plants in high nitrate and soft water, so I determined it was easier to raise my KH rather than trying to walk a tight line on NO3. No improvement on A Reineckii. I have also tried Jobes sticks under them, and I have placed stems under each type of light in different parts of the tank. None of that makes any difference. That some people grow AR like weeds blows me away-I can't figure out how they do it.
My goal is to keep L. Glandulosa alive, keep most lower leaves, and get A. Reineckii to grow. I don't even care if it grows green - just grow! I'll worry about turning it red later... Top leaves are red, so I assume its getting enough light and iron.
Should dim the LED further? I estimate right now that halfway down the tank I have over 100 PAR directly under the fixture, based on BML website. At substrate I should have around 50. That should be enough to keep lower leaves of stem plants, right? Can AR grow at substrate at PAR of 30? (Plants are 1-2" tall) I wonder if the light is causing other plants to out-compete AR for CO2 and/or nutrients.
Could I still be short on CO2, even with a 1.4 pH drop? Even with some margin of error on test kit I should still be at least 30 ppm. I don't see any fish distress at level I have, and I could probably turn it up more. I don't think its a distribution issue, with two reactors, lots of mist and noticeable flow around all plants.
Could substrate need replacing? I have 8 year-old fluorite, 4" deep.
Is there anything off in fertilization? I have two API nitrate kits - one at least eight years old and one bought this year. Readings are beet red on both of them. Should I try to get NO3 down to 10-20 ppm, or does it not matter if I have way over 40 ppm? Does the fact that the tank looks worse 5-6 days after W/C suggest I'm dosing too low on anything? I get GDA on glass, but not a single spot of GSA. Thankfully I have no BBA or hair algae either. If ferts were the problem, two weeks of full EI should have shown improvement. I get Leibig's law, but it seems like I have a lot of everything yet the plants aren't responding like they should.
I can add some photos later, but the AR looks similar to many other photos posted by people having trouble with it - lower leaves rotting away with some algae on them. Solution is usually more CO2, but I have tried that to no avail.