Join Date: Sep 2005
Location: Arlington, Texas
I have the exact same tank, 2 AC HOBs, wpg, etc. as you (48x18x24) except I am using 2x65 CF lights and have just recently noticed pinholes in some hygro and lobelia that I had recently added from my overgrown co2 tank. The leaves on the lobelia are turning yellow around the edges. I also added some echinodorus bolivianus chain swords a few weeks ago for the foreground and they are losing a few leaf tips and have some browning around the edges. My Bacopa, Mermaid Weed, Crypts and Cabomba Furcata have been in the tank for about 1 year and have no holes and are still growing well.
I recently starting dosing K along with Ca and Mg to see if that helps. Since the problem seems to be in the old leaves in my tank it may take awhile to see if it helps. I have enough fish so I know I'm getting NO3 and P from poop and fish food so I am also assuming it is a K problem. I am using Seachems Equilibrium weekly now which adds the K, Ca, Mg and some Fe. The extra Ca and Mg is probably also needed in my tank since I don't do frequent water changes and have a lot of cherry shrimp in the tank.
I will be following this thread closely since I am having a similar problem.