Try this. It is a sort of compromise approach for less than ideal conditions.

If you have a fan set it up on low but not right next to the plants. You just want it to move the air lightly around the room so 5-6" away.

Put the dome back on but stick some toothpicks or something like popsickle sticks in the corners and a couple along the sides to hold the dome up about 1/2 inch or so - may take some adjusting. This will still allow some condensation to form but not as much.

Some will cut slits or holes in the dome but that ruins the dome and makes it difficult to adjust if you cut too many but you can do that too.

A couple of times a day remove the dome completely to allow for fresh air and shake off the condensation inside.

Hope this helps.

Dave

If you have mold they are too wet.The lack of air circulation doesn't help but that's not the main cause and it is not essential until the seeds have sprouted.

A pot will dry from the top down. when the top is dry there is still moisture underneath and if you water them you are back to the same too wet conditions.Your plants probably died from damping off rather than being too dry.

The solution;

When you start the pots wet the soil before filling the pots, so you know it's wet right through. It should be moist but not sopping. Squeeze a handful and just a little water should come out. If it's too wet add more soil.

That is for future sowings. Now you should just spritz the tops with a spray bottle when you think it's too dry--just enough to dampen the seeds. Put the humidity covers back on. In a while if you have lots of moisture on the cover then carefully lift it and shake it out over a sink. You can tell the plant is wet or too wet by the amount of moisture condensed on the cover. If you see mold sprinkle the top with cinnamon. In fact it probably would be a good idea to do them all as a precaution. I have found that containers with the humidity covers need very little water, except the odd spray.

When the plants sprout take off the covers and get a fan on the plants to improve air circulation. Make sure they are dry about half way down before you water--stick your finger in the soil-- and then water from the bottom just until it shows wet on top

Ok, are we talking about germinating here, or growing on? There's a difference in what's needed. Once you see that the seeds have sprouted, it's time to remove that dome. If you are trying to use the dome to maintain the moisture level of the soil, then there's something wrong with your setup that the soil can't last 7-8 hours without drying out. My best guess from the info you've provided, I'd say you have the lights too close. The 'get the lights as close as possible' rule really only applies once the seeds are fully sprouted, and then they should be a few inches from the top of the seedlings. So, the seedlings should be about an inch tall or more when fully sprouted, and then the lights a few inches up from that. I usually keep the lights about 5-6 inches from the flat, and even then, they will dry out the soil within about a 36-48 hour period. If your bulbs are really 2.5 inches away from the soil, that's quite close, and you'll never be able to maintain proper surface moisture (as you've discovered). If I were you, I'd pull your lights back up several inches (probably about 6 inches from the soil), bottom water and lightly spray the surface, and you should be able to maintain a moist but mold free surface for at least 24 hours or more. Try it out, see if that helps!

What seeds are/have you started?

and what stage are they in? seed, germinated, true leaves?

Like Sleepy said, that has a lot to do with it.

Keriann

Sorry.. I see that they are seedlings, not seeds.

Oops..

What kind are they? I know with my impatiens, I had to mist them 2-3 times a day until they grew 4-5 sets of true leaves.

What color is your mold?

I know I had bright green fungus growing on the top of my petunias and they ae fine.... quite large and ready to flower actually.

It may be that your basement already had mold spores in it and you created a new place for it to live.

Can you get a few in a different room with lights and see if that helps?

Keriann~

Dave -- Thank you for your suggestions! I will definitely try to prop the dome a little and keep a fan going nearby.

Oilpainter -- I acknowledge that damping-off may have played a role in killing the seedlings, but I did notice that they were fine when the soil was moist ... and in the morning, when the cell had tried out too much on top, they had fallen over (and not from the stem base -- it was more like an overall drooping).
I've also heard a bit about this cinnamon trick -- I'll have to give it a try!

Sleepy33 -- Thanks also for your advice. I may need to pull the lights away from the not-yet-germinated seeds, especially the poor surface-sown ones!

Keriann -- You were actually right! I have both seedlings and not-yet-germinated seeds going right now. Swamp milkweed, purple prairie clover, sweet indian plantain, scabiosa, some violets, dill, and prairie coreopsis have sprouted. Milkweed is doing the best right now, just about to show first set of true leaves! I'm most worried about the violets, which are sprouting slowly and sporadically. They're so small, I'm afraid of them being consumed by mold. Same with snapdragon and joe pye weed seeds, which are extremely tiny and surface-sown.

As for fungus:
So far I've mostly seen a white haze of mold on my soil. Very subtle-looking. But strangely, I've also noticed many chunks of perlite exhibiting a coating of yellowish to orange-ish mold! What in the world!? I took tweezers and removed as much of the perlite from the soil surface as possible.

I've also just started trying to overnight my seedling/seeded flats in my bedroom with a fan on to help keep the mold down. And sadly, I have no other place to set up my lights. :(

I never had any success starting seeds indoors until I bought some seed-starting sets from Gardener's Supply. They are Styrofoam cells which sit of top of a capillary mat that draws water from the reservoir underneath. They water themselves and all I gotta do is turn the lights on and off. (and fill the reservoir every once in a while). They've lasted nearly 10 years.

Just an idea for next year. Obviously most people, especially the talented ones here, do not need to use these systems, but I struggled for years (YEARS) with either dried up or moldy pots.

(I did not mean to sound like a commercial)

Maureen

Just a thought but hydrogen peroxide can be sprayed on mold to kill it and turns into water shortly after. It is a mild bleach and shouldn't hurt most seedlings. I use it in my carnivorous terrariums when mold appears and carnivorous plants are very touchy when it comes to water purity.

That orange yellowish in the perlite is not mold. It is the perlite absorbing iron either from the soil or from the water. It should not affect the plants, but you may try filtering your water if you have a brita filter.

Won't help this time round, but when you start your seeds next time - use STERILE packs and soil mix. I reuse mine every year - day before starting seeds, dip the packs in a chlorox/water mixture and air dry.
Damping off is from soil that is too wet. I leave teh domes on until the seeds have sprouted. Then depending on the size of the seedling, I either put under lights with or without the dome. I use cool white flor. tubes and have them about 3 inches above the top of the seedling.

Hmmmm ... I may have discovered something.

I planted two different "crops" of seeds on Sunday. One was in my regular, plastic 32-cell tray that I've been using, with the same seed-starting mix I've used for my other seeds (Schultz brand).

The other crop was planted in a Burpee expandable-pellet tray (with 50 pellets). Both trays have both been in the same exact conditions, and yes -- I kept their humidity domes on (thinking that exposure to my basement air was causing the mold).

Today, I found that the flats filled with Schultz soil were moldy after only two days. The Burpee pellet tray, however, is spotless!!

Perhaps Schultz has been causing most (if not all) of the problems after all! I'll be keeping track of my trays' progress. I know it's been only two days, but I find this discovery pretty interesting.

Did you sterilize the 32 cell tray after your last round of seeds and before this round? If not, the mold/fungus you had before will still be present in the tray and will re-form almost instantly, even in fresh seed starting mix.

I'm wondering about the use of cinnamon when that white/grey fungus or mold is seen on the top of seedling pots. I'm having a hell of a time with disease, dispite changing from seed mix to milled spaghnum moss. I have used a product called Actinovate in a mist to spray the seedlings with, but it doesn't help much. I've lost so many seedlings it's pathetic. I've never had these problems before. The seedlings I'm struggling with are Thunbergia, morning glory, castor beans, melanpodium, vigna, sunflowers and climbing spinach. Please, any advice??