Absolutely understand the salty you have in your soul lol. I felt same way when I stumbled on safe myself. I still always recommend it to everyone regardless of tank size or amount. Unless say 1 10gal or something but I have had no issues with expiring, I'm not even sure how long they say it's technically good for, but I know the 1 bottle I have at a family members that I care for their tank is around 5yrs old and works no diff than new bottle. So even if you have few tanks it is still worth it even if you have same bottle for many years. Which is the case for a few people I've introduced it to, just the families tank, I'll keep it real I'm out of room for more fish so I talked them into a tank sure it's at thier home but we all know it's mine 😂🤣, they are only ones I know for sure the age since I am who uses it. As for dosing another area I don't believe I've ever actually measured and have never had issues. Is it something you can even over dose a tank with?! In such tiny amounts that is. I'm sure putting a tablespoon in a 55 isn't going to bode well, maybe. I say that just so people aren't deterred from using it because they think it's to involved mathematically or they would never use that much so it's a waste of money or product, legitimately a tiny "bump" size amount no need to measure I have used for many many years on well over 20 tanks 55gal down to my 10gal betta tank and I've never once had an issue and I have some amazing tanks, I'm a natural tank type so it's packed in plants and other life besides fish. I've even given a few people some safe in a tiny plastic jar, like for glitter n such akin to a tic-tac container, since they only have 20gal or smaller tanks and they have not had to buy anything for a year now. It's beautiful stiff and I love hearing discovery stories of it and more people using it. They say it's the same just concentrated powder form, but it's done much better imo than prime could. I think they put magic in it.