Answer: Determining exactly how often to water can really be a challenge. Even slightly moist pellets will look darker than completely dry pellets. You'll want to provide adequate moisture without over-saturating the soil and the best way to do this is to water from the bottom so the peat pellets can soak up the moisture. When they are completely saturated, drain the water from the tray (as many times as it takes, as often as it collects). Watering from the bottom keeps moisture off the tops of the plants (wet stems can contract a fungal disease called damping off).
When I'm watering my seedlings, I look for a few dry threads of peat on the very top of the pellet. If everything is still plump and moist, I don't water. If I see some dry peat, I water thoroughly. Hope this method works for you, too.
Or, if you have an extra peat pellet you can use it to determine how much water it is holding at any given shade of brown. Simply saturate it thoroughly, allow it to drain, then compare its color to those that you have planted. You can pick it up to judge weight and squeeze it slightly to determine how much moisture it is holding.
Best wishes with your new little seedlings.
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