Simply Meaning,,, Don't Pour the Whole Bottle over the pipe. Lol. If its just a 115gph pump I'd use it sparingly when applying. But Just enough to get a Good Seal...
For higher PSI, and when talking about putting one in the basement, to another level, etc. I'd put a, "Decent" amount of Glue on, and Make sure its on Nice and Good. and Tight... and give it Ample time to dry... This is when Leaks and " Things ", that go wrong, typically occur. When dealing with Larger Diameters, and Higher PSI, there is a Larger Surface Area and More Room, for error to occur, and sometimes Actually making them more difficult/longer for them to bond. ...
With a Small Nano, you can almost get away with Just pressing the Pipes together, I have in the past, Ran a 5g - 10g, for 2 months, using No Glue. Nonetheless, This was a random Tank, a few friends and I, just Threw together for fun.
Given' if it was a "Tank" of mine, I'd deff' of applied the glue.lol
So to summarize, I'd recommend, not going overboard on Glueing pipes for something such-as, a Nano. Just get enough on there, to thoroughly, Coat all Contact Points, and to be sure it adherer's to each other. Less chance of Fouling the water and other factors...
Sorry to Confuse anyone, Take what I say In Stride.lol
I understand, What I may call " a Lil ", may Greatly Differ from what you call a lil'. But Just My, " 2 Cents ".lol