My Betta has fin rot so today I bought a 28L tank + heater and filter and transferred him to it.

Now, ive put some of my sand substrate from my main tank in a old pair of tights and put it at the bottom of the tank + ive taken a piece of the filter media from my canister filter and put it in the new one, is this going to be enough to keep the ammonia + nitrite at bay? Or will the tank still need to cycle?

Btw ive put a pair of tights over the filter output to reduce the flow as it was blowing the betta around, is this ok?