Thanks Diana. I have a phosphate test kit for my reef tank so I should be able to figure out what's needed. I figure with the flourite I have plenty of iron. I have actually had some pieces of flourite stick to my magfloat.
I don't get the EI thing. That much water change just seems like bad management. You're throwing away too much of what you just added. I would rather measure and get to know my tank.
And testing is a waste as well, depends on what trade offs you want.
A better term is providing non limiting nutrients
rather than "waste".
Few hobbyists test consistently, and if you use those test kits to rely solely on dosing, then you should also calibrate the test kits, other wise you are simply guessing they are correct and are no better off.
That is human factor, nothing to do with the plants, and such management issues cause issues. "Waste" can easily be reduced slow and progressively till you have just barely non limiting levels.
If someone relies on test kit results, they should use reference standards, just like they use with pH meters to calibrate those, particularly for N and P which test kits are off by 5-10ppm typically.
EI can dial in that range easily. Which was my point over 13 years ago.
So the test kits really offer no advantage in terms of accuracy really.
You can modify EI also.
Most use plants as their test kit, and adjust the dosing from high non limiting, where you are sure that the nutrients are independent, down slow and progressively. Once you see a negative sign in growth, you adjust the dosing back up to the next higher amount.
Water changes are not "wasteful". If wastewater is a concerned, add a shower aerator, get a better toilet, use a cup when shaving/brushing teeth etc, and what you do with the wastewater is also key afterwards, mine goes on the landscaping plants outside. It might be more labor, but there's little labor difference between 10-25% water change and 50%, particularly if you use a siphon python like hose to drain and refill. For smaller tanks, say a 20 Gal, I can do a 50% water change is under 4 minutes. 10 Gal of water is spread out on the landscape outside. That's not waste. Landscapes and lawns suck up far more water and waste than any aquarium. Even if it goes down the drain, the water treatment plant reuses it again.
I can reduce the water changes wayyyyy wayyy down this way by progressively reducing the dosing by volume without any test kits.
But I like to stay on top of things more and it's much easier and simpler for hobbyists to do than test kits.
Some use test kits to adjust their EI dosing, but here again, this does little good with calibrating the test kits. Well, if you suggest you do not need to, that the test kits are "accurate enough", then the error range is no better than EI.
So you end up wasting ferts and having poor management eitherway.
Still, water is extremely cheap, much cheaper than any set of test kits might last over an entire year. Ferts are extremely cheap
and maybe used for landscaping plants with wastewater. If reducing waste and energy is really the deal, then we all likely should not ever even keep aquariums, but atlas, here we all are
So there's some acceptance of waste. Also, since you read EI, you should read the confusion and myths surrounding the method, it's not meant to be written in stone and filled with the exact type of misunderstanding that's gone on here (and many other places from time to time with other folks).
I prefer to go a more sustainable approach myself.
This starts with less light, which is the worse waste product we have and causes the most issue for management.
You want less waste? Use less light, add "just enough light". Then you use less CO2/nutrients as well and waste less of both, and have less algae and still nice healthy, but slowed growth.
It's also fast, simple, cheap and easy, all good traits for management of aquatic plant tanks.
Discus folks do this also, they do 50% 2x a week often. Are they wasteful for keeping and raising discus?
Are we not all wasteful in keeping aquariums in that regard????
There's a trade off we accept, so then it's an issue of labor, technical abilities, motivation to test or do a water change, cost and management
No doubt, tech abilities EI beats the snot out of other methods.
However, even here, using a sediment based ferts helps. ADA As etc, or soil, worm casting etc, add and then dosing is much easier, you can add less to the water column and trim things down since the sediment provides a back up.
I fully suggest this type of holistic approach.
You'll note I discuss light, using less etc, and sediments, and CO2 management, nutrients are not independent of these, any method that assumes that will have many issues.
Overall, dosing is easy and simple, some want to complicate the heck out of it and test and fiddle with a dozen parameters, maybe only 3-4. Still , I have a nice clean vibrant tank after a good sized water change, what do I have after spending a 1/2 testing 4 parameters?
Not much really.
You can try these method sand see what you really think, let me know after 5 years if you still test regularly an dose according to those results. Not very many do.
You work through what these trade offs are for you personally, think about them, think about your own personal habits, will you stick with it? Most do not. This is much more a human issue than anything to do with dosing methods.