1. yes, no

2. You certainly don't have to, but with the responses I've gotten for
the last 10 years, you can test and chase nutrients with test kits if
you want, depends on how much algae and how you want the tank to look.
Some don't mind a little algae and not do their water changes or don't
have plants that nearly as picky. But it works on those.
There are trade offs, but the water changes + adding the nutrients back
is rather simple and very flexible with many light choices.

Pythons, or other DIY water changers make water changes fast and
painless. It's cheaper than other methods, you add 3 things _once a
week_ in your case(you might split the traces into 2x a week).

With a large fish load and an unwillingness to do water changes, it's
like cramming 10 people in a bathroom and not flushing the toilet for
weeks.........
If you want success, I will say you will need to reconsider your
approach.

Say add lots of CO2, add K2SO4, and some KH2PO4 and some traces. You
might need a little KNO3, maybe 10mls of traces 2x aweek.
60% weekly water changes, should not take that long, maybe 20- minutes
to do the water change and refill.

With a high fish load, well...........I suggest something other than a
large pleco.

3. Both are Red algae. Totally different genera, staghorn often comes
with high fish load tanks, (associated with NH4), BBA with low CO2. If
you do not add CO2, you need to stop doing water changes and
ramatically lower your fish load.

If you add CO2, you need to do many weekly water changes and add plenty
of CO2.
That's your choice. But you do not get both, there's trade offs
involved here.

I don't tell folks what they want, I just help with what they want to
do.......

Regards,
Tom Barr

Regards,
Tom Barr