While No Water Change can work in the short term and offer some water change flexibility, I would say for most people including me, No Water Change can cause problems in the long term.
Problem #1
Adding supplements like AFR or A- K+, only replenish estimations of consumption. Over time some elements increase over time, and others decrease over time. With every passing day the composition of the tank water slowly diverges from natural seawater.
When I use A- K+ and ESV B-Ionic 2-part:
Potassium, Chromium, Fluoride, Manganese, Iodine, Nickel - Decrease over time
Bromide, Strontium, Molybdenum, Lithium, and Selenium - Increase over time
When I supplement using individual elements based in ICP-MS and use ESV B-Ionic 2-part:
Bromide, Lithium, Selenium - Increase over time
I think Bromide and Lithium are coming from the Calcium component of the 2-part. I recently switched to the Randy Mix using
BRS pharmaceutical grade Calcium Chloride and Soda Ash with TM Part-C. I’m thinking Selenium is coming from the fish food.
Problem #2
You can make the argument that dosing individual elements with ICP-MS allows you to seemingly supplement all elements that are low, but the problem then becomes the elements that are elevated. There is no way to selective reduce them.
Problem #3
The potential exists for some organics or other toxins to accumulate that cannot be removed with things like activated carbon.
Life took me away from the drudgery of performing water changes for a few months. With trace element dosing I’m happy to report the corals look great, but I’m well aware there can be a ticking time bomb in the shadows. Example - During this time the Lithium in the high consumption SPS tanks increased to around 2,000 ug/l! If you really wanted to fix this and restore the tank to NSW levels, it would require around 90% of the water to be replaced, and this is not easy. This is like 10 20% water changes, or 5 40% water changes!
While many people get away with no water changes, there are risks and you have to be a little lucky to pull it off. The corals you have, what you feed, how much you feed, what you dose, quality of make-up water, etc all play a role, and have to align to provide long term balance.
If you want to better understand exactly what’s going on with trace elements in your tank, do not use a standard ICP test. A test coming back with all zeros for things like Iron, Manganese, Cobalt, Nickel, Chromium, etc is not very helpful. The highly sensitive ICP-MS test must be used.