Re: Water changes in non EI tanks
We assume that the test kit measures what is occuring in the plant.
we also assume the form of the nutrient is bioavailable, most test kits measdure total alk, total NO3, total PO4, not the bioavailable forms.
Do you measure all the needed growth parameters?
You can apoproach it this way, but my and a number of folks that are extremely observant in terms of plant health, Amano among them, suggest at least 25% weekly changes for optimum health. You can get by and do pretty well without doing water changes. But use less light and you will find it much easier to balance things. That's your choice in the trade off.
You do not have to do weekly 50% either.
25% 2x a week etc
25% a week etc
As far as why you cannot do 90 gal was not stated either.
It might because you want to use a lot of RO water and the storage is not available. A number of potential reasons pop up with this issue.
You see what you really think and give each routine some time and see what you think.
Every CO2 enriched tank I've ever owned did better with frequent water changes, as well as fish only tanks. I'm not alone with this one either.
One thing to deal with and that cleans the tank up well, removes dead plant material etc is a good thing, mulm accumulation over time is not good either.
You assume it's well controlled, but there are many things the test do not tell you. The control is also determined by the test and you testing each parameter.
Mg, Ca, NO3, Fe as proxy for all traces, PO4, K+, KH.
By the time I measure that, I've done the water change with a python or a simple hard plumbed system(this would take about 30 minutes total, some less depending on the pipe sizing for drain and refill).
I do not touch buckets except to toss pruned plant scrap into.
A python water changer is not a troublesome thing to use.
With larger tanks, making the water change process simple is a very wise and time saving feature.
Once in place, it's no longer a chore or an issue. I much prefer to work on a tank when it's 1/2 full, pruning is easier, so is cleaning, replanting, not getting nearly as wet etc. If you scape and garden significantly, over time you'll agree, Amano does the same thing.
You prune while draining and refilling.
Hoses are not hard to use and reach most any place in any home.
You can certainly extend the times you need to do water changes(I';ve gone 4-6 weeks without water changes using EI), but if you feel you can do this and don't mind the trade offs, go for it.
I've done it in the past, many have, I think it's a PITA and some luck is involved. Also, do not assume the test kits, even the good ones are always right, each kit has it's own set of errors, you need to calibrate the test kits as well if you plan on relying on them solely for the dosing routines.
You can go months with non CO2 tanks and easily a month with Excel dosing. So if that is your goal, it's much easier to hit that balance and avoid test kits, tanks still look very nice also.