The Planted Tank Forum - View Single Post - How do you dose ferts without measuring them first?
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post #15 of (permalink) Old 12-10-2012, 03:10 AM
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Originally Posted by bikinibottom View Post
T And with my saltwater tanks I would only test for the first month to see that the tank was cycling properly, and then once every several months just to make sure that everything was still normal (although I think I've always been able to tell if something "bad" was going on in the tank based on the behaviors of the critters and growth of the coral).
Since marine salt mixes cost and take an addition step to mix, many use test kits to avoid cost and mixing hassles. FW folks do not have this issue for the most part.

I still do large water changes and KISS for marine systems. One added cost/step vs all the other stuff to avoid it.

I read the EI explanation here:

and if I understand it correctly, I'm looking at weekly 50% water changes and dosing forever. And that the dosing will be highly dependent on the level of light you have in the tank, which is hard to determine accurately without an expensive PAR meter.
No, 50% is entirely arbitrary.
You can chose whatever % or frequency you chose, if you increase the frequency or %, the error associated with the range will go down:

95% 2x a week water change san ddosign thereafter: likely within a very tight range of small error.

If you do 20% once a month, then the error will increase a great deal.
Wet's dosing calculator and graphing function lets you explore those models and scenarios.

Another misconception:

A simple method to reduce the % water changes and dosign:

Since I didn't get into the hobby to test, change water constantly and spend money on fertilizers, I guess more to the point of my question is whether dosing is necessary at all. I read Walstad's book, and in the chapter about plant nutrition she concludes that a low-tech tank with a soil substrate doesn't need water changes or the addition of fertilizers since many of the nutrients/micro-nutrients come from the soil and are replenished to a lesser extent by the addition of fish food. I realize it's been many years since she wrote that book, and that some of her conclusions may have changed since then, so I wonder if this is one of them.
Thanks again.
That's works well for a non CO2 approach, I dose once a week to the water about 1/10-1/20th EI and forwent the soil sediment. I do no water changes.
They are very different goals, no method will be all things to all hobbyists' goals.

Some have different management, CO2 drives growth 10-20X faster than non CO2, there's no CO2 competition between species of plants(so you can grow them all together, in non CO2 tanks, you really have a very hard time growing several species well together, most are "easy" weedy species). A well maintained garden and lush landscape is much harder to do, but it can be done. Most lack the patience frankly.

All methods grow plants, the difference is at what rate. EI is mostly a simple method to rule out limiting factors due to nutrients for any light amount. CO2 is still dependent no matter what method you chose(except the non CO2 method, but even there, CO2 limitation plays a defining role)..

Tom Barr
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