If anyone is interested, I found some huge organic watercress with roots and even had the dirt still attached! I just chucked it in the tank and the fish swarmed it. It's right up to the lights floating. I'll consider repositioning it later over the weekend, but looks good so far. I also looked around online and found some articles mentioning that I should grow long-grain brown rice. So, I found some of that in seed form and I also found something that said mixed rice. It's got a bunch of different kinds of rice seeds, super expensive though at $5/lb. I only got a tiny bit, but that's like a few hundred seeds that hopefully something will grow.