If you decide to razor out the silicon wait a week if you can bear it - the drier it is the easier it is.
I have bought 2 tanks that had heavy handed silicone jobs and have painstakingly razored out the excess from inside and out and while it takes hours and hours, it's worth it not to look at green algae gunk all down the edges a few months later.
For the best 'shave' though you will need a very flexible sharp razor, I've tried all but keep coming back to the double sided very thin dangerous ones. I've used masking tape on one side so it's safe to hold. If you scrape it on the glass edge it will get blunt so if you need to do that (I did in places to scrape off bits) be prepared to use another one. You can definitely get that kind of razor in a shaving type shop (rare but there might be one in Wellington), or I bought mine on the offchance in the supermarket, they weren't there when I went back. I have never found one of the old fashioned flexible one sided razor blades except in copious amounts on Trademe.