Okey dokey my dears... It's time to confront the question of the week and give it an answer!
This week we're hearing from Tasha, and I *think* I understand the question, but I'm not positive. Tasha, you referred to micros, but then went on to explain fodder; are we just talking fodder here? I wasn't sure where the micros came in. Just to clarify the difference betwixt the two, microgreens are a leafy vegetable such as cabbage, kale, radish, and peas that are grown in soil until 14 days after germination, and then normally saved for human consumption. These are fancy little greens that sell for a hugely high price to restaurants. Chefs love 'em. Fodder on the other hand is barley or wheat (the two most common grains; you can sprout anything, but nothing grows like these two) that is grown "hydroponically", meaning there's no soil; you just keep them in drained trays until you have a mat of "grass" which you feed to livestock. You don't sell this stuff to restaurants. ;)
I'm going to guess that we're talking about fodder here, so that's where I'm taking this conversation. :) You asked how often to water fodder, and then stated that you're having mold problems. I can relate. And I'll bet an acorn to an oak that anyone else who has ever done fodder will raise their hand and agree that they've had the same problem. Oh the mold issue... Don't worry, it's fixable.
First off, make sure that the grain in your trays is no deeper than 3/4 of an inch. Any deeper and you'll just exacerbate the molding problem. Any thinner and it'll dry out too soon, and then when you get it wet again, you face mold, or the loss of the entire tray due to the germ dying. (yeah, this is sounding like a really fun project, huh?) If you feel that your seed depth isn't a problem, then next look at your drainage. There should be NO standing water, EVER. I repeat, NO standing water, EVER. When you water your grain, all liquid should drain out within twenty seconds. If it takes longer than that, then you need more drainage. Someone gave me "pre-drilled" trays once, and those things took almost a minute to drain. This seemed great at first; I was able to fill each tray to the brim and then walk away, letting it drain slowly on its own. Or, that was the thought anyway... Since there weren't enough drainage holes, there would be too much moisture hiding in the cracks and crevices; puddles sitting in the low spots where there was no drainage hole. After two days in the high 80's I had to throw ALL of it out. Mold. Lots of it. As to how often to water, I do it 3x's a day when it's hot outside (like, 80F and up). Anything cooler than that, and I find that 2x's a day is usually fine.
Now, suppose your drainage is fine, and your depth of each layer is fine. Now what!? Mold is an extremely common problem during the summer; doesn't matter how you do it, you're most likely going to have mold issues because it's hot, your grain stays moist all the time, and each pound of grain has thousands - if not millions - of bacteria spores coating it, which is what causes your mold. So the key is to deal with the bacteria that's present on the grain itself. How do you do that? There are a couple ways.
1. Skip the initial soak during hot weather. Normally you let your grain sit in water for 12-24 hours before you put it in the tray. Skip it, and put your dry grain in those trays. I don't completely understand what effect this has on the grain, but someone gave me this tip when I was having issues with mold back in August and it worked well for me.
2. Put a "glug" (1/8 to 1/4 cup) of apple cider vinegar (raw, with the "mother" in it) in the water that is soaking the grain. This method you would obviously only use if you wanted to keep doing that initial soak (which some feel is beneficial in breaking down enzymes). Or, you can do a capful of bleach into the soak water. Either one should work; these *should* kill off the bacteria that's causing you problems. I say "should" a little hesitantly because nothing is for certain with this. I've had both options work really well for me, but I have a different climate than you most likely.
If you're still having mold problems when they're growing, and you're not growing a huge amount of fodder, you could try watering with a watering can, and putting a bit of ACV or bleach in the can once a day (I would really recommend the ACV during the growing period) to keep that bacteria at bay.
Hope this helps! Mold can be such a frustrating thing to figure out.