You may be able to grow HC if you do daily water changes.
Say 20%.
You will still need ferts for the plants.
Shrimp food alone will not be enough.

Regards,
Tom Barr

You are right, my second strip is 10,000K, not 1000K. I am changing it to 6,700K, so I would have 2x6,700K 14W lights over my tank.

I do have a regular maintenance routine, including weekly 50% water changes, EI fertilizing, daily Excell and 10 hrs/day lighting period on a timer. So I believe I am doing right in all these areas.

I think my problem is with lighting. Maybe the 10,000K bulb is not doing much for plant growth? In that case I would have only 14w usable light over 20 gal. I'll see if changing it helps.

I had a 10gal tank before with 2 screw in 10w 6,700K CF bulbs, with no fertilization, and I think I had better growth then, although I still had algae problems.

I use one 10,000K bulb and one 6500K bulb on my 32g. I have switched the 10,000K bulb out with a 4500K bulb and haven't noticed any difference in plant growth between the two bulbs. However maybe certain plants are affected differently. Recently I added aluminum foil to my reflectors since what I had stock was really a very poor reflector, and I see a big difference in growth now. Not sure if that would be an issue. Unfortunately I'm also seeing thread algae appear as well, but so far it's not totally out of control and is concentrated on plants that are closest to the surface which are easy to prune away. I also increased my photoperiod to 12 hours so this may be part of the cause of the algae, it may have little to do with the reflectors. But I believe that the reflector change definitely increased the amount of useable light in the tank by probably at least 10 - 20%.

Clarissa, I suspect the photoperiod of 12 hours is a bigger problem than the light increase from the aluminum foil reflectors. And, about 10-20% is the increase I would expect from that change.

Yes, I agree. I just wanted to see what would happen, since previously I had only kept my tank on an 8 - 9 hour cycle. I think I'll go down to 10 hours and see what happens. I've also noticed that my plants are growing differently - more leaves are sprouting from the same nodes where they used to grow pretty lean and spread out. I have a feeling that that change may be more due to the increased light, than the longer photoperiod.