Originally Posted by scoupland
My planted tank is 48"L x 24"D. I have 2, 48" TrueLumen Pro LED 8000K lights on the tank. They are 17" from the soil surface. I started the tank with the DSM and the plants grew very well. The Stauro, in particular, grew like crazy and I even sold a bunch of it. Once I submersed the tank, I have notice about the bottom quarter of many of the plants do not do well; that is, the leaves die. The top 3/4 of the plants look healthy and are growing well even though I don't see any pearling. Another thing I noticed is that the Stauro grew flat on the soil when the tank was DSM. Now that it is submerged, the Stauro is growing tall. I am running my lights for 7 hours/day at full strength. I am running CO2, auto E.I. dosing, temp is 77, pH is 6.7. Am I not getting enough depth penetration with these lights? Should I just run my lights longer? What if I add a third 48" TrueLumen light strip? Or, maybe I should go with different brand of light. I have some ATI T5s but I want to stick with LEDs because of the heat issue in this room.
2 TrueLumen Pros should be enough light for your plants to thrive as you saw with DSM. From my experience in taking par measurements underwater and out of water, there's a +/- 3 micromole discrepancy. It doesn't fluctuate very much unless the water is cloudy. With that said, it's not light intensity that's causing the plants to melt underneath the new growth. The largest variation between underwater and out of water (DSM) is the CO2 saturation in water compared to out of water in DSM. I believe Tom Barr mentioned several times before, it's usually competition for nutrients and co2 is what usually causes the plants on the bottom to melt. Since you're using EI dosing, nutrients could be eliminated and the issue points to CO2. I would recommend raising CO2 a notch and see if that helps. Definitely keep up the EI as well.
My method for optimizing CO2 is simple. No drop checker, no co2 meter. The best indicator are the fish but I highly recommend doing this when you're around your tank. Raise the co2 a notch and keep an eye on the way the fish react for at least the next hour or 2. Do the same thing the next day and the next day and so on. until the fish start swimming to the surface, then turn it back down to the setting you had the day before and that's usually the right level.
Hope this helps!