Thanks , the tank is an ongoing metamorphasis.
The Pothos survives long term underwater, I have a thread called "Pothos In your tank Easy Peasy" that explains how to condition it submerged. A couple of things to know.
The roots have to establish well for them to survive in the water. I used ammonia during cycling to let them feed off that. Takes about 2 weeks to show roots. Over time some stem sections will get 'weak' or turn pale. Snip 'em off and it will help strengthen the new shoots. Shoots that grow completely submerged tend to be 'crisp' and easier to snap. Periodically a weak leaf will discolor or split, getting holes. Just snip it off. The roots on mine are everywhere. I just let them tangle on stuff and leave it be.
If you get algae just wipe the leaves off. Check out the other thread for details. Pothos is a low light plant. I actually have both the ivory and golden pothos in the main tank. In my 40s I have pieces that have completely transitioned to all water. The leaves are small, round and compact and the shoots dense in a clump.
You can always just toss in some new Pothos periodically. Rinse and serve. Make sure it has lots of good roots and you'll be fine.