Any bubbles that form can be sucked out using a piece of airline as a syphon.
Poke it thru to the bubble and suck it back out.
I do that with one of my HOB filters when it gets an airlock in it.
Clarrie Stead, deceased, X of the Levin A Soc., use to make tanks with a tunnel.
A common base had two octagonal tanks built either end with the sides facing one another having a cross over tube of about 150 mm square.
Look quite different.
One of his favs, especially for auctions, was one built as a boat.
I don't know how practical they were, but they were eye-catching, and must have taken a lot of time and patience building them.
Mabe his widow Hoya, if she sees this, could give us a little run-down for her first posting, on this.
Alan 104
ps. I don't think there can be many members who remember these now.
mmmmm
Al