Is the word も for "seaweed" still used?

[Fearabhata]

When it comes to the wordstem 藻、it finds its way in words like "kaisū" and "sūrui", which both means seaweed.

My question comes from the old saying, clear water breeds no fish
Or in original: 水が清ければ魚住まず。
From the book I read it refers to as
[...] もがらなどがあるから, その蔭に魚は隠れて成長するのである。
Though to be honest it is kinda hard to read because there is no kanji usage.
The thing is, would a modern age japanese person understand me when saying it like this or think of me bananas

注
もから
藻の茎 (Stem of the seaweed, as for near the roots)

 

[Toritoribe]

Is the word も for "seaweed" still used?

Yes.

The thing is, would a modern age japanese person understand me when saying it like this

Yes, of course. Indeed もがら is not so common, but it's understandable enough from the context. It's also because I know から/がら (e.g. 芋がら).

もから

Sorry for nitpicking, but it's もがら, not もから, as in the excerpt you quoted. Rendaku occurs on か here.

水が清ければ魚住まず

Also, the proverb is actually 水清ければ魚棲まず (が is unnecessary. 住まず is not wrong, but 棲まず is usually used for this proverb). If the first half is 水が清ければ like modern Japanese, the last half also should be 魚は棲まない. The reading of 魚 would be さかな in this case, unlike うお in the proverb.