Pond Advice

Any pond experts out there?

I have a bucket which I euphemistically refer to as a pond. It has 1 very large frog, 2 newts, 4 snails and a zillion tadpoles:

I love the tadders, the ones who have grown legs are really cocky – they are the ones who are sitting on the bit of wood. They sit there as they can breath which the other tadders cannot and it is as though they are lording it over the undeveloped ones!

Recently the pond has started to smell and the water looks thicker if that makes any sense? I pulled some weed out of it the other day as it looked a bit congested, and the smell was indescribably awful.

Is there anything I can/should do to improve it? I’m worried that the water may be bad for the tadpoles etc?