I have the same problem, I can't see those little nails well enough to clip them myself so what I've done is to put bricks in the cages that they have to walk on.
I have 2 R680s connect together with ferret tubing so they have to step on those bricks to go from room to room. They do that all the time, run back & forth. These bricks really do seem to keep those nails trim because I don't get scratched up.
If you don't have a set up like this you can put the brick under the water bottle so that they must step on the brick to drink.
I don't use bricks that have a rough surface that would scratch the skin on their feet but it does seem to wear down the nails enough.
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PHRatz