I just bought 2 African Dwarf Frogs. They're in my 10G quarantine now, with an Aquaclear 30 using a fluval pre-filter on the intake. To prevent damage to my frogs and them getting a leg or arm sucked into my main tank Penn Plax Cascade 700 Canister Filter, do I need a pre-filter on that intake too? The fluval pre-filter won't fit if I do.