Thanks, that's what I thought. Now I am thinking I have some insects I don't see and the spiders feed on them.

I know there are red spider mites, but in my collection I see small black spiders. Should I be concerned? Do they eat the plants or other insects?

I thought the opposite, the soil should dry quickly to prevent rot. I live in NJ. These are house plants. My mix is equal parts of regular soil, coconut coir, pumice, and coarse sand. The pots are from a regular clay. When I water, I add about half an inch on the entire surface. I think most of the ...

I have been following the rule to water when dry. I have some soil/pot/cacti that get completely dry within 2-3 days. Would you say it's OK to water every 3 days in some cases, or there is some kind of minimum?

I am afraid of too much rain, possibly wind, and also insects. I might experiment with a few plants.

Still looking for advice on how many hours to run the artificial light? Should I match sunrise and sunset? Or it does not hurt to add a few ours before and after?

Thanks, again.

I added a timer to my setup. How many hours, at what time, should I keep the lights on? Currently, the sunrise in my area is at 5:45 a.m. and sunset is at 8 p.m.

Following your advice, I ended up with 2x54W 4 ft. T5HO. I also lowered it closer to the cacti, without blocking the sun. IMG00100-20130506-1518a.jpg How would I choose which cacti should be under the light? Should I be concerned that they may not be used to 16 hours of "sun"? Some cacti, ...

Yes, now that I think about it, it was more round initially, similar to the M. gracilis picture.

Is it possible that the shape is determined by the fact that it is still very small? It's ~2 inches high. It has as much sun as everything else on the windowsill.

It is still young, but maybe somebody can ID it...

Thank you! It will be exciting to watch how it grows.

Thank you! Another identified cactus!

2nd is definitely NOT "Fairy Castles". My 2 cents

Yes, it looks similar, but matanzanus seems to have a tall cephalium. The one I have seems to be flat.

Echinocactus grusonii? But I've never seen so many spines.