3rd Grow and have a Co2 Question

Hey guys so I decided I wanted to go bigger on my 3rd grow then I did in the past.
1st grow: https://www.rollitup.org/newbie-central/409744-new-member-1st-grow.html#post5326483

2nd grow: https://www.rollitup.org/grow-room-design-setup/433528-new-setup-new-plants-but.html#post5808185

This time I've purchased a 4x4x8 Sunhut, 600 watt hps with yield master II hood and digital ballast, ph meter. Even got a ventilation system all set up. ***pictures at bottom** Now I'm on the last few purchases such as the light yoyo, co2 tank w/ regulator, and the babies themselves. But my question is about the Co2, I have a tank called an aluminum 74 that I used to use for oxygen while scuba diving. Is it possible to get it filled with Co2? I'm kinda weird about taking it to a store and drawing attention before knowing. Only source of Co2 I've used in the past are the Co2 pads that release it.

I doubt they would fill it considering it was designed for a marine application. And if you are paranoid, then why would you do something abnormal like having a scuba tank thingy filled with co2? Be less paranoid and make a clearer decision, like buying an actual 20lb co2 tank and then having it filled with co2. They aren't going to ask what you are using it for because they don't care, and if they ask tell them it's for your co2 powered sex machine thats fucks you in the ass with a 14'' black dildo. This way you can be sure they won't ask you anymore questions about shit that isn't their business.

HAHAHAHAHAHA. Okay. Figured I'd make an attempt to save a little cash. Is 20lbs a pretty regular size tank, what places usually sell them other than hydro stores(the one near me just jacks up the prices)? Isn't 14" just a wee bit big?

Oh, places like a welding supply store, medical stores might have it. You want a 20lb ALUMINUM tank with a handle. Get a used one because some places only do exchanges instead of fillups, so if you exchanged it you won't ever see that nice shiny tank again.

You could tell them it was a 6'' white dildo if you want to sell it, but the point was to just shut them up, not make them think you are actually going to use it to fuck yourself, lol.

Are you just venting the light or are you exhausting the room? Have you looked into co2 monitors?

the light didnt have a 6inch fitment for the exhaust, so i bought an inline fan off my buddy that will help pull more out of the whole tent. that is installed in the ceiling and venting up and out the roof. i have a hydro meter that i think shows co2 levels also. thanks for the advice. anything else i should try and get? i am thinking because the space is only 4x4 im prolly only going to do 8 plants even though i want 10

***Bump*** Got a big bale of Sunshine mix #4 and 8 Master Purple Kush clones are gunna be arriving at my house next week..... finally