Gidds:I thought you were supposed to wear LESS weight in FW? :06: I know 20lbs is too much for me in SW so I don't think 19 is any good for FW. I wasn't using an AL80 since I was just in the pool (although I normally do), I think he said it was a 45? :06: My head only feels highly positively bouyant when I kneel on the bottom and I'm in an upright position, I don't notice it when I'm swimming horizontally. I still think I was overweighted because I kept face-planting on the bottom of the pool when I'd go fully horizontal and stop kicking. A little air in the BC stopped the face-plants. Why do my feet keep floating? It's really annoying, I don't want to swim around in trumpet fish position.
Yes you will use less weight in fresh water. Multiply the entire weight of you and all of your gear including the gas in your cylinder (.08LB/CF) by .026. This number is the swing based on the difference in specific gravity of the fluids 1 vs 1.026. You can go fresh for salt or salt for fresh since it adds up to a rounding error at that magnitude.
For the sake of doing skills and stuff in a pool beng a little overweighted is probably to your advantage. The real divng takes place after the pool so you might as well just be down to do skills and drills.
With an empty BC and a near full cylinder you should pretty much hit bottom anyway. I assume the exposure protection was minimal in the pool. Adding a little air as you state would do the trick, you will need less air as the cylinder pressure drops.
Correct weight and correct trim are two different things. Once you get into consistent gear do the bobbing at eye level test with a 500 PSi tank and get the right weight to be barely positive at the end of your dives. Armed with this weight you can distribute weight in your BC features and on your belt. Don't forget to maintain a consistent tank mounting position, this can make a huge difference. Remember that a heavy face may be light feet so you may want to have all of your weight towards your belt and or your tank band near the cylinder crown. Let the dust settle and remember your physics classes.
Pete