Its so easy to put in access ports in an aluminum tank. Cut a square
hole, get 2"wide aluminum strips the same gage as the tank walls and
install as a sister flange using bolts as attachment studs, epoxy coat
the sister flange to the tank and then simply line everything, the
original cut out square used as the closure manhole/handhole. The
typical 100 gallon square tank in most boats are such that a human arm
can reach entirely across to the other side from an access port.
Honestly did you ever see a LARGE access port on a rotomolded tank that
didnt cost almost as much as the tank without an access port?

Without access ports there is NO way to get inside and mechanically
scrub off any biofilm (calcyx) ... and if there there is any calcyx
remaining, simple sanitization methods simply will not work. Access
port ARE simpler easier and cheaper to install /add to an aluminum
tank.

Mmmmmmmm most ballfes in fabricated metal tanks inthe marine industry
typically only have 5%-10% of the projected cross section open to
prevent 'sloshing' . A rotomolded tank would probably consist of
mostly deep Vs to accomplish the same. A rotomolded tank with the
typical baffle area and baffle 'exit' area form by deep Vs would be
absolutely preposterous while having little useful internal volume in
comparison. Sorry.

:-)

problem is on a normal baffeled tank of any size (under the size a man
can crawl thru the baffles) is painting it with a brush or roller is
next to impossiable, unless the tank has an inspection/work port in
every space between baffles. It's a great way to go if your building
tanks but expensive to do right. And roto mold tanks can and do have
baffles. They are made by molding deep V's into the sides of the
tanks.

Joe