its pretty easy. Just get a bunch of razor blades and remove the silicon inside the tank(not the stuff between the glass) and I mean all of it the glass must be perfectly clean. Once its all off, rub it down with alcohol.
Then just apply a new bead of silicon and smooth it out and let it dry for 48 hours.
For smoothing it out, some people say use pop-sickle sticks. I just use my finger, but dunk it in soapy water first so it doenst stick to you so much. Also dont press it into the joint just run your finger along it to smooth it out.
For clean edges you can either tape it off, or just use a razor blade to trim it back once its dry.
If you cleaned it well enough thats all you need to do.
