Drilling is not an option since it's stocked and running it would be way too much of a hassle.
I've used smaller shops overflow on a 75 years ago but I wasn't so concernedly because there wasn't much flow and never had an issue.
I saw that the 1200 has 2 U tubes but thought maybe if I added a third it might help if one breaks syphon?... would you recommend that?.... I had an aqua lifter pump around the house somewhere maybe make the third U tube out of PVC and drill a hole on top for the aqua lifter pump to at least guarantee 1 tube with full syphon?
My sump is gonna be a ghetto makeshift large storage container of some sort. So if syphon fails there shouldn't be a ton of water for the pump to use to pump back up into the tank if syphon fails.... it will prob run dry.
I'm using a storage bin only to pack in media, not for more water volume and also so I can drill it and use the drain in the sump to drain the excess wastewater from my drip system.
First things first it is possible to drill a tank with livestock in it. Trust me it is not hard at all. Look into King of DIY on youtube
Second no I don't recommend adding another utube from 2 reason
1) I don't believe there is room for another one, since both ends of each tube needs to be submerged, the clear side of the overflow box where the bulkhead is located, the middle section is always filled so the siphon won't break, it is sized for 2 utube.
2) even if it fits, the more utube there is, the more flow you will need to push out any air bubbles that gets into the tube by accident. Or else it will trap air and potentially cause the siphon to break. You are having a higher risk having a third utube because you are trying to minimize risk, that's counterproductive
Aqua lifter can get the job done. I can't find any around me since they are discontinued.
And yeah you could drill your sump and drip water into your tank to achieve auto water change. I have done it before works like a charm. But I personally moved on using a water reservoir and pump water from it instead. Due to an accident with my city doing some work on its water piping and some contaminants got into it, it wiped out one of my tank's livestock since I was out of town for a few days. That being said the chance of this happening to you is very very low.
I didn't drill my tanks is simply because my tanks are tempered. Or I would have definitely drill them, and I would highly recommend anyone who has non-tempered tank to drill their tank as well.
Btw besides using traditional bio media, please look into the anoxic filter by dr Kevin Novak. Its abilities to filter amazed me and it doesn't use a lot of space. The only issues will be locating the raw materials( they are dirt cheap just hard to find the right kind depending on where you live)