I have an Aerogarden 7 so it only extends to twelve inches high and my tomato plants are at the lights at 6 weeks and need to come out. They grow much faster in the Aerogarden than they do on my heat mat with a grow light. The roots are rather long at that point and I use a chop stick to try and seperate them as I remove each plant. I fertilize them with a liquid seaweed extract and have never lost a plant. I have never tried to use the 25 plant Styrofoam insert to grow to grow all tomatoes. It would be a lot of work to get them all out successfully and the sponges are rather expensive.

I start my tomatoes on Feb. on a heat mat. I read somewhere on here to start you tomatoes in an inch of dirt in the bottom of your pot.( I use yoghurt cups ,i drill drainage holes in them) Then i add dirt as the tomatoes grow up. I Have done this for two years and it works great ,without having to mess with lights. I have an aerogarden i use to start peppers. There isn't enough space for the amount of tomatoes i grow. The photo is of some of last years tomato plants at about eight weeks.

Karen58, I have been considering the heat mat as an option. You are in zone 5a which is even colder than where I am which is helpful. A couple more questions - 1) how long do you leave them on the heat mat? 2) They look pretty big at 8 weeks (and very healthy!) but it's probably still too cold where you are to put them outside. When do you put them outside?

Blender13, thank you for you point about the amount of work and cost to use the Aerogarden. I was thinking about using the seed starting tray rather than regular pods but you make a very good point. Separating all those roots could be a disaster.

Thanks!