Looking at Juwel's website, the Lido has the same type of filter as my old Rio 125.
I removed the filter from my Rio with fish in the tank. Do it during a water change so there is less water in the tank. If it is full, you'll probably cause a tidal wave.
You'll need a sharp knife that has a bit of give in it, I sacrificed an old kitchen knife. Mine had eight blobs of silicone holding the casing to the glass, four per side, two at the top and two at the bottom. Start with the top blobs on the easiest to get at side. Pull the top of the filter away from the tank and saw through the blobs at the top, then repeat for the lower blobs. Now you'll be able to get at the less easy side to do those.
This did leave black silicone on the glass. I removed those with a Stanley knife blade held almost flat against the glass. Very carefully!
Be careful not to touch the corner sealant.