Well they sell wicking material at most greenhouse supply stores online but a cheap substitute is anything cotton, small towels, pieces of felt, loops of cotton clothes line. The t-shirt should work as good as most anything.

The main problem I have found with wicking is you have to monitor it closely at first and make adjustments in the amount of it to keep the soil from getting too wet.

I rigged up several trays a few years back when an out-of-town emergency came up and cam home a few days later to drowned plants. As long as there is water the material will wick it up whether the plants need it or not.

Dave

Here is a link that might be useful: wicking material discussions and links

Hmm, my seed starting mix contains 50% potting soil, 25% Coconut Coir, and 25% Vermiculite. Will that retain too much water and drown my plants?

Depends on exactly what you mean by "potting soil". If it actually contains soil then it is definitely to water retentive. Only soil-less potting mixes are recommended for use in containers.

If it is actually a soil-less potting mix, which is a very different thing from potting soil, then it should work fine. But I can't tell what the effects of adding the other ingredients to it will be. You'll have to do some experimenting with your set-up to see.

Seeds, while germinating, and young seedlings need to be kept lightly damp/moist, not soaking wet. Soaking wet or standing in water rots seeds and drowns young roots.

Dave