Hi jeeplassie, I have never seen any church with aquariums, although I haven't been to that many in the first place. 
We do partial water change of 30~50% once a week, and it is highly recommended for the health of the fish. It is necessary for getting ride of the nitrate buildup, as well as to restore water buffer and minerals. It is why the larger the tank, the more water we have to remove and to restore.
Do you mean custom made fish tank or custom designed aquascaping? 
I actually plan to get a custom made 90 gallon tank eventually. I have specific requirement for the dimension which I can't find in typical 90 gallon.
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