[neilshieh]

I've noticed that my l. arcuata (not sure on ID) has been growing very poorly recently. Any idea what kind of deficiency this is?

 

[neilshieh]

The plant in the first photo is Ammannia crassicaulis which is a notoriously difficult plant to grow. It also grows quite slowly and seems to take a very long time to recover from nutrient deficiency problems. Here is a PlantFinder entry for a related (and similarly picky) species: http://www.aquaticplantcentral.com/forumapc/plantfinder/details.php?id=118 you can read up on its finicky behavior there.

This particular species often stunts in the way yours does and can do so for many reasons. It is sensitive to GH, and doesn't do very well at GH over about 6-8. If you recently added calcium to the tank then that is likely why the leaves are twisted up like that.

It can also develop twisted leaves when nitrogen deficient, though you should see some of the older leaves deteriorate as well if it is nitrogen deficiency. How do your old leaves look?

What ferts are you adding, what is the GH, and any other test kit values you have available (not pH).

Can you take a few more photos of new and old growth?

When you have corrected the problem the plant will take at least 2-4 weeks to start recovering.

Oh awkward. well atleast now I know the plant's ID :bounce:
I suspect it's the gh that's been causing the problem
Here are my water params the last time I tested on Feb 17
nitrate: 10
nitrite: 0
ammonia: 0
phosphate: 5-10
ph: 6.8
kh: 7
gh: unknown

But here's what I do know about the gh. Fremont water's gh is 10 but the thing is I've been using seachem's neutral regulator+discus buffer which is a phosphate based buffer that lowers ph and softens water by precipitating calcium and magnesium. However due to some algae issues I've stopped using the buffers so that I could have more control over my phosphate dosing (didn't dose any because phosphate buffers caused my phosphate levels to be pretty high already) and I've been doing water changes with water treated using seachem safe. So the gh must be rising which was also when I started to notice that the plant wasn't looking so good. Previously it grew spectacularly and was a nice red. The older leaves are fine. just the new ones look twisted.

My setup is a 29 gallon with 3x23W cfl bulbs in worklights on top of a glass canopy. I can grow HC and l. sphaerocarpa just fine. Ferts are based off of wets calculator for EI dosing. Instructions say 3-4 times a weeks but I only dose kno3 and k2so4 and a squirt of plantex csm+b 2 times a week.

 

[neilshieh]

I'm tempted to dose the buffers again but right now I've got GSA on the walls and it's annoying not being able to control the phosphate levels in my tank. Question... are there different types of phosphates? or are the phosphates from the buffers usable by plants?

I might use ro/di but need to think if it's worth investing in. Otherwise might just pull the plant.