Absolutely agree with this! Sand = big no no. Put him on the paper towels for now til you know what's wrong with him. Once he's better or deemed ok by your vet, you can use aspen or cyprus mulch if you prefer something more natural. But you won't be sorry you used the paper towels in the meantime.
And do get the dimmer and accurite. You won't be sorry you did this either.
He may not have an impaction, but that sand could be causing other issues such as scale rot or a bacterial infection. Sand harbors all kinds of bacteria even when you think it's really clean. Just an fyi....