The DAP is expensive for that small quantity ($6.99 for 82.8 ml), compared to a tube for a caulking gun (~ $4.00 for 300ml). The small tubes are perhaps more convenient for small jobs, but I usually have an unfinished tube available for those things. Silicne has a shelf life and while it may still work beyond that date if the tube is unopened, there is no gurantee. Once it has been opened, the time to use it is relatively short, even if the tube is well ealed.
I have actually used house brands for the last 15 or so years which are usually a little cheaper, and also say ideal for aquariums on the label.