I think you are certainly are on the right track.
Yes, we all can get away with fewer water changes. Many did/still do fewer water changes than weekly. Some avoided them altogether, some did it with test kits, some without.
Dosing ferts and using test kits to balance is nothing "new", and PPS certainly steps on the work of others in it's claims to be as such(EI, list of levels and parameters and PMDD). Here's something we wrote back in 1996:
http://www.barrreport.com/estimative-index/2386-old-version-1996-1997-list-levels-parameters.html
I suggested testing and water changes.
If you are helping folks rather than pushing an agenda in this hobby, yo will use several things to help them, no just relying on test kits alone and thinkign they will actually use them consistently and will have no errors. CO2 is a huge issue and large water changes are a good method to see if there is a CO2 issue.
I myself suggested less water change but we tended to include water changes as a safety valve rather than as some great benefit, still, many did pretty good(some went several years without a water change I personally know and I myself went 9 months etc).
If you cannot do the water change, you might not want to keep CO2 enriched tanks. This is a trade off, not something inherent in the method of doing water changes vs using a test kit and adding ferts(this is certainly PMDD philosophy, not PSS). Still, no ferts are really required for non CO2, no test kits and no water changes.
No algae either.
That 1st tank above is over 2 years old, no water change yet, water is tad yellow, but that's fine.
Do not assume that drop checker is okay, nor pay much heed to the pH.
KH likely drops in such tanks with fewer water changes, this causes folks to think the pH is fine if stable. Drop checkers are slow to respond, not a bad general tool and easy to use, but do not put that much trust i them
I do not use them myself nor pH.
Another simpler method is there, watch the plants.........but it requires diligence initiallyand experience.Somethings that are lacking with some and with new folks.
So this will lead to errors for some folks and some will kill their fish etc.
At lower light, this is an easy target to hit.
BBA itself will not merely die once you restore good CO2 in many cases.
Lowering the light is awlays a good idea if there's a plant or algae issue.
Why might that be?
Nutrient demand or CO2 demand?
CO2...........it's 45% of the plant's biomass and measuring it is hard to do accurately, it changes not day to day but hour to hour and can range from 0-1ppm to 35ppm in less than 1 hour.
Given all that, I think keeping an eye on that, using water changes as a safety valve, good care over time yeilds pretty good results.
Look at ADA, they suggest low light, rich sediments(less dosing issues), daily dosing, good CO2 and large weekly or more water changes.
This makes it easy for folks. I agree with that. Can you get away with fewer water changes once the tank is established? Yes. It is more risk, some do not mind it.
I make water changes easy as possible for myself, or clients.
Then it's not so m uch a motivational issue, or labor intensive. I turn a valve to drain, turn another to fill. I can clean, prune and work inside the tank much easier when the water change is going on. If I uproot and move things, then all that organic material is cleaned out etc.
Running the tank lean is fine, but it does not save anyone from BGA/BBA, and using less light will help the leaner you go.
I think many are still enamoured with PO4 limitation and are unwilling to concede that it does not induce algal blooms. This business has gone on for over a decade now and the critics are trying to play a semantics game, rather than using results and testing. Anyone that's done this for a long time knows, they are not guessing, that PO4 limitation does not stop algae, rather, things like CO2 are the larger driving factors.
After having it occur many times, they can validate it and also modify and help folks using PPS(how might they know this?), there's no rule that says you must do EI weekly for water changes, or dosing the full amount, it can and likely should be modified.
But no method works well if you have issues with CO2.........and algae and plants tell a lot and are more accurate and a better "test kit", they measure exactly what you are interested in.
You can use some excel, water changes, remove a few things and bleach, trim plant leaves etc, keep the light lower(and whenever you leave for a few days), do the same old thing and get the tank whipped back into shape.
Folks have had bad BBA in every dosing method, this does not imply that it is PO4, NO3 etc. Even radically limited PO4 tanks have it. The moral here is really to look more into things beyond a certain agenda that tells you what you want to hear and claims to have all the answers.
No such method.
So you look at the overall factors that drive plant growth, see if you can induce algae etc if you really want to confirm things. Then you can understand every method and how they are pretty much the same, but importantly, now you can modify and build one that best suits your methods.
Some folks like high light and trimming often.
Many do not.
Some hate test kits and simply will not do it.
Some do not mind.
Most of these issues are human factors to control things and avoid work.
I can automate a water change and make it far easier, I cannot do this for testing the water and I am still left with many unknowns that the water changes removes.
It takes effort to test for me, and I need a reason more than day to day keeping of planted tanks. So I ask interesting questions(at least to me), and test the ideas on purpose. Then after the results I no longer need to test further really.
I have my answer(hopefully) and generally 5 more questions now that it has been answered.........This does not lead to simple easy nice answers(the kind many want to hear)
I am more likely to do a water change than test. Most aquarists fall into this group(more social science and the human factor, not aquarium issues).
If your goal is few water changes, I'd stick with the lower light, switch to ADA AS, CO2(or not), lean dosing(the ADA AS will help there and give more wiggle room, another back up source of ferts) is fine as the deamnd is much lower due to low light, less CO2 demand and flux-> less algae, longer times between increase/decreases in nutrients etc.
You should be able to get away with 1x a month water change without too much issue(mostly do them after a big trim). Perhaps longer depending on the plant species etc. You still should prune and top, add some Excel if you see any BBA, keep things clean, clean the filter often.
Remember that reduce filter flow ates occur when they get clogged leading to less flow in the tank. This can also lead to reduced CO2=> BBA. Neglected tanks and clogged filters, even high bioloading also some to induce BBA.
Consider these also and stay on top of things, it might take a few weeks if you are agressive, but it should go away, particularly if you focus on less light and good CO2.
Regards,
Tom Barr