Food size should typically be no larger than the space between their eyes..5-6 small or 3-4 medium crickets a couple times a week is fine. Small meal worms are fine..just don't let one get all the worms, cause they will gorge.
As for algae, it's typical in a new tank to get diatom blooms. It should go away. Stringy algae either means too high light or nutrients or not enough filtration. Pictures would help. You will get it also on new wood that is constantly wet and it will dissipate.
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