Who does water changes and who does not? What % of water do you change and how often? I have a 125 gal and a 55 gal sump. The real total volume is around 150 when you count the rock work and what I have in the sump. I use a 32 gal brute trash can to do my changes. I fill it up to 28 gal. That is about a 20% water change. I try to do that every 2 weeks. Is this too much at one time or also to often. I know they say small volume and more often but I don’t have that time.
My system is about 150 gallons total volume. I try to do a 10 gallon water change every weekend. Of course i skip this process every once in a while. I don’t get concerned over skipping changes every once in a while. If i miss a couple weeks in a row i will sometimes do a 15 gallon change. So my water changes weekly are less than 10% (about 6-7%)
I have a heavy bio load in my opinion, with about 10 fish total but I don’t feed heavily, I give them frozen food once per day occasionally skipping a day.
I grow macro algae in the sump and run a skimmer 24/7 so my nutrient export is controlled by those two things not my water changes.
My reason for water changes is simply to replenish the micro nutrients I don’t test for (molybendum, strontium, ect…)
I dose:
soda ash (alk)
calcium chloride
magnesium sulfate and chloride mixture
Iodide
Potassium nitrate (when nitrate is too low/less than .5)
5G once every 2 years 
tank has never been happier than when I stopped doing changes
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Adam, what type of corals do you have in your tank. Do you dose anything?
I have a bit of everything. No dosing, but kalk in my ATO.
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I dont do changes either. My tank is coral only right now. All softies. I actually dose potassium nitrate and reef chilli for added nutrients… never in a million years would i have thought i would be doing that when i started almost 20yrs ago! All that said i do siphon off 5gal of detritus water (bare bottom) every few months and i just top off with fresh water and some salt.