declension spellings

I have a simple question about spelling:

We are in the 5th chapter of Christiana (book 1) and I am having trouble figuring out how to spell the last 3 words in the declensions.

For example: (first declension)
aqua.....................aquae
aquae...................aquarum
aquae...................aquais....or maybe aquas or aquis??
aquarum................aquaas....or aquas??
aqua.....................aquais....or as noted above?

I am not sure how to make the changes when the word ends have vowels in them.

filia..........filiae
filiae........filiarum
filiae........filis?? or filiis?
filiam........filias??
filia...........filis??

Is there a simple rule that I am missing??
Thanks.
KellyJo

[CarolinaMom]

I believe the correct declension of aqua would be as follows:

aqua............aquae
aquae..........aquarum
aquae..........aquis
aquam.........aquas
aqua...........aquis

As for "filia," I checked several websites and this is what they all said:

Declension of filia

filia...........filiae
filiae..........filiarum
filiae..........filiabus
filiam.........filias
filia...........filiabus

It is irregular.

If you google "latin declension of filia" you can find them. If I'm wrong, someone please correct me.

Elizabeth in NC