By frozen food I mean blood worm. Tubiflex, daphnia, artaimia etc they sometimes sell it in fish retailers. They eat stuff once every 2-4 days it's easy to tell when they need feeding they have a very slow metabalisum, in length aproximatly 1-2 ft depth they don't swim at all so hight isn't an issue a good gavel is about 1cm cubed(smoothed) I wouldn't surggest getting the gravel from river but If you think it's clean enough taking in mind farm run off then smooth rocks are good to get from it you can get moss spores etc which newts love. from them and to get land parts rock/ gravel piles (secured not to fall over) can be usefull and a simple floating log will do. As long as the water is regulary changed for toxins and the
Guppy is large enough then it's a good idea the calcium will brighten there colour!