It may be too late to answer... but:
Sprout_Question said: They have all sprouted and are about 1 - 1.5 inches long.
I was going to plant the sprouts this week.
They seem older than I let them get when floated. I usually put them in soil once the sprout/root and all is a quarter inch (5-10mm) long. If left in water, I see little mold hairs (water mold) that start growing and the seed sheath (that brown part) is always going to start to decay/attract mold. Water roots are different than soil roots- so I don't see the advantage of leaving them in the water if they are going to be growing in soil. The water method adds a transplanting step as well, and I lose a few during that process.
That being said- the water method is like a science experiment! It's cool to watch! Sometimes older hipps seeds (not fresh seeds) might do better floated, I've heard.
These are mostly species Hippeastrums- all floated and then transplanted to individual cells this spring. I'm pondering transplanting the biggest ones, or maybe wait until spring. I won't encourage dormancy this fall by withholding water.
Sprout_Question said:
Since my amaryllis sprouts have now been exposed to mold, what should I do?
Since molds are EVERYWHERE, I think most plants in soil have been exposed to fungus repeatedly.
Transplanting them probably will take care of it without a problem. If you let them dry t0 much to take care of the mold, you risk putting them into dormancy or not making the transition to soil. Cinnamon can be tried, but I usually use a fungicide spray. Start with a sterile seed starting mix and clean pots or trays.
These are hybrid hipps seeds I just spread on the top of moist seed-starting mix, covered with plastic to keep them moist, then keep warm and in bright, indirect light. Again, start with a sterile seed starting mix and clean pots or trays.
Yes, some mold is on some, (see photo, extreme bottom left) so I have propped open the top to let more air in and dry a bit for a few hours each day. The mold is attacking the sheath, which is dead tissue, not the green leaves/roots, so far. I'm not too worried.
I'll spray them with some sulfur-based fungicide or my new favorite fungicide -salts of phosphorous acid, as it functions as both a curative and preventive treatment, and then acts as a fertilizer as it breaks down. I use it for my cuttings frequently, as cuttings are a race against the attack of fungus! I also use it as a bulb dip before planting my hipps bulbs.
Trade names are:
* Monterey Garden Phos Systemic Fungicide
* Reliant Systemic Fungicide
I can't say if cinnamon is effective. I guess if you try it, tell us how it worked?