Frog spawn in garden pond

I have a small pond in my garden which looks dirty and has a lot of leaves from the tree above and is quite shallow (however room to add more water) - tonight I have noticed a frog and frog spawn in the pond. Is there anything I can do to make it more habitable for the frogs? Do I need to top it up with more water? And should I try and clean out the water and garden debris? Thanks!