By sucker fish do you mean chinese algae eater? if so then it will be fine. Marbles are not a good substrate by themselves because it is hard to clean arond them but if you put in an inch of sand or gravel and press the marbles 1/2 way down into them it will work. Take your time stocking the tank so that you do not get an ammonia spike or you can lose all the fish. It is better to get the filter and heater running before adding fish and remember to dechlorinate the water.
