i've heard of feeding chinese water dragons dogfood. just check the ingredients on the bag, if they're close to what your fish would eat, then go for it.
the cheaper/more common variety of dogfood will usually contain mostly corn or vegetable products (thats how they make it so much cheaper than the expensive kind) if your fish would be safe eating these, with a little bit of red meat flavoring, i'd say go for it.
one problem is that dogfoods sometimes have lots of preservatives, which might not be healthy for fishies. also, dry dogfood falls apart quickly in water, and will spoil the water in a heatbeat if you dont keep an eye on it.
hope that helps.