making Resevoirs (DIY acrylic aquariums?)

[nka]

In small size, your better of using 250 hockey card holder or cars case (I dont know the name, but those for showing car in shelf?).

[Feign]

In small size, your better of using 250 hockey card holder or cars case (I dont know the name, but those for showing car in shelf?).

Of course, in the US we call them Baseball card holders, so it took me a moment to get what you meant.

On an entirely different direction, a straight walled measuring cup (that you don't plan on using for food!) would probably be a good quick and easy first choice as well for easy calibration.