saltwater to freshwater?

[clownknifecrazy]

so i just recently bought a 75 gallon tank but it was a saltwater and i want to convert it to a freshwater tank but the tank has a hole in the bottom of it and i want to know if there is any way to patch this hole or even if there is anykind of freshwater filter that will use the hole in the bottom of the tank

 

[Andrew McFadden]

You can still run a sump as in a wet/dry filter