A lot of conclusions can be made from this statement. The most sensible and critical conclusion you can come up maybe, is knowing the time for the fish tank to be full. You can determine this by dividing the volume with the rate.
30 gallons * (1 L / 0.26 gal ) * ( 1 hour / 58 L) = 1.99 hours
The fish tank can be filled up in approximately 2 hours.