well i downloaded and inspected this set of icons, I Think they are quite decent, i agree with what some body sayed erlyer, needs more tiers of icons, but still do able, full, one third emprty, half empty, one third left, empty, if you felt like it.
even as it is, its still useful, it dosent glow too much so its passible as water, yet makes a good (refillible mana potion? idk) also each one only has less then 25 kb in total your map for 3 variations, which is quite decent for eny kind of survival maps.
il give these sets of 3 icons 7.5/8 out of 10 (could be a 8.5 or 9 if you added extra tiers of liqiud amount)