Day 6 still sounds like very early days, the yeast and proteins are still in suspension in the beer (which is a good thing) and is normal at this stage. I would say leave it another week/10 days, and then test the gravity of the beer two consecutive days. If it's the same both days then bottle it. It's very likely to be cloudy when you bottle it too, as there will still be yeast in suspension (it is this yeast that 'eats' your priming sugar and carbonates your been in the bottle or keg). Eventually the yeast will eat all of the sugar and go dormant and drop out of suspension giving a yeast layer on the bottom of the bottle (perhaps after 2-3 weeks in the bottle) and it will just get cleaner and clearer from there (unless it is something like a Wheat beer which is best drunk young and cloudy) leave it longer in the bottle and it will get better and better.
You could dissolve a leaf of gelatine (supermarket will have them in baking aisle) in 200ml or so of boiling water. Allow to cool and add to FV. Wait a couple of days.
You could also cold crash it if you have enough room in your fridge.
It's a fining agent. I don't know the science but I know it does work.
When adding, keep good sanitary practice, add at a temperature similar to the wort, wait a few days to clear.
As fuggled said, day 6 is a bit early to judge clarity. Even bottling day can be too early. Conditioning in the bottle for a fortnight, then a day or two chilling in the fridge will improve clarity further.
I think most types of finings work by binding to the proteins, bits of hops and yeast that cause the cloudiness, therefore making large heavy particles that easily drop to the bottom of the fv
I think most types of finings work by binding to the proteins, bits of hops and yeast that cause the cloudiness, therefore making large heavy particles that easily drop to the bottom of the fv therefore creating clear beer
Hmm... even if you've the same three days in a row it's too early for the beer to be clear. If the reading is low, 1.010 or 1.012 or lower then it could be ready to bottle but I wouldn't expect it to clear for weeks. You could add a fining like gelatin if the fermentation is finished and then bottle... if the gravity is still 1.020 or something like that just give it longer. It won't clear until after a few weeks in the bottle.
The simple answer to the OP is to leave it until it clears or is nearly clear. If it's cloudy, irrespective of whether the SG has bottomed out, the yeast is still working.
I now usually leave my beer at least 16 days in the FV before I package and by then they are pretty much clear but will still have enough yeast to carbonate.
And if it's a straight forward kit without grain additions there is, in my opinion, absolutely no need to use gelatin or anything else to get clear beer. Packaging nearly clear beer to start with, followed by time and gravity will do it for you.