When introducing small fish into your large aquarium, it may be a good idea to cut back on the water flow until the tiny fish gets acclimated to its new surroundings. Intense water flow can push the small fish into a particular corner, and sand dwelling species may have a hard time staying on the bottom. Once the fish has become comfortable in the aquarium and is eating, starting ramping up the flow slowly. If you have multiple pumps turned off, turn them on one by one over several days instead of all at once. If your pumps have controllable flow rates, either through an external or an on board controller, slowly increase the speeds until they have been restored to their normal flow rates.