To change or not to change

[vetteguy53081]

How many gallons do you change out daily on your large tanks?

2 gallons daily or if busy every other day, in fact just got done with water exchange

 

[newreef1]

2 gallons daily or if busy every other day, in fact just got done with water exchange

So like 30% a month. Huh never thought about that, instead of pulling out my pump and doing 30% once a month, could have two empty water gallons and just pull 2 gallons out, replace with 2 new gallons water lol and I guess the filters remove the extra detritus anyways.

 

[jmichaelh7]

How about just driving your car for 5 years and top off oil when it runs out. Never do a oil change

 

[Randy Holmes-Farley Verified Community Expert]

What% WC do you recommend for a 200 gallon tank for monthly WC. I like doing WC, but honestly every week is difficult, I typically do about 25% every 3-4 weeks so like once a month. What would you suggest?

There's not a lot of definitive data, but I generally recommend changing 1% daily is a decent plan. I did that on my system which varied from 250-350 gallons total volume. That is most readily dose with an AWC system. In my case, it changed water slowly and steadily, ~20 times a day, 24/7, 15 minutes of pumping each time.

 

[Randy Holmes-Farley Verified Community Expert]

How about just driving your car for 5 years and top off oil when it runs out. Never do a oil change

My car doesn't have oil. lol

 

[Dburr1014]

people argue that it stops things from building up but it doesn't. If you're doing 100% every month, then yes, maybe it does. But somehow people think 25% per week equals 100% in a month. That isn't how percentages work. 25% per week still is 25% of the total water per month. I think water changes are a waste of time. It will never decrease build up nor help replenish trace elements. Easiest way for me to think of it is putting up 20% of your check every two weeks is still only 20% of the total amount earned.

This is flawed I think.
NO3 build up in the system. Let's say it's 20ppm per month added. Change 25% of water every month. 20 - 25%=15ppm. Add 20 ppm the next month. 15 + 20 = 35ppm minus the 25% water change 35- 25% = 26.25ppm

If no water change you would be at 40ppm in 2 months.
I realize it's not entirely how it works but it is pretty basic math.

Also, if your trace elements fall every month, where will they come from? No water change, maybe add them in 2 part of you have the demand. That is all.

 

[Crustaceon]

people argue that it stops things from building up but it doesn't. If you're doing 100% every month, then yes, maybe it does. But somehow people think 25% per week equals 100% in a month. That isn't how percentages work. 25% per week still is 25% of the total water per month. I think water changes are a waste of time. It will never decrease build up nor help replenish trace elements. Easiest way for me to think of it is putting up 20% of your check every two weeks is still only 20% of the total amount earned.

Sorry but no. You can't say something is "building up" while you're seeing a reduction in quantity and the point of water changes isn't to achieve ZERO buildup in a tank anyways. That's obviously never going to happen. The point of water changes is to reduce buildup to levels that are safe for livestock. Let's say if a reefer has a gradually increasing amount of nitrates while only doing 5% weekly water changes, increasing the water change amount to 10% a week can absolutely put the tank on a trend to reduce nitrates to very low levels over the course of a few months. That's reduced buildup. Yes, nitrates will still be present, but they will be LESS, not more, which is the definition of "build up".

 

[snackpack]

people argue that it stops things from building up but it doesn't. If you're doing 100% every month, then yes, maybe it does. But somehow people think 25% per week equals 100% in a month. That isn't how percentages work. 25% per week still is 25% of the total water per month. I think water changes are a waste of time. It will never decrease build up nor help replenish trace elements. Easiest way for me to think of it is putting up 20% of your check every two weeks is still only 20% of the total amount earned.

But that's not how it works either. You're diluting the existing water with new water.

Here's an example of dilution. If I do a monthly 20 gallon water change on a 100 gallon tank, your logic would mean that I've change the total tank volume over 2.4x in 12 months. In reality I've only replaced 93.13 gallons over a year.

 

[Key Largo]

OK, a nice discussioin about the pros of water change. But my original post was asking, specifically, aquarist that for some reason or other eskew water changes or do them rarely. So unless those people really dont exist, Id like to know how that routine evolved (or devolved as the case may be). What observations, events, articles etc. lead you to stop doing water changes? I read "havent done a water change in 2 years", "no water changes going on 18 months, everything happy". Really? Why? Are you never going to do a water change?

 

[vanguard]

That isn't how percentages work. 25% per week still is 25% of the total water per month.

Your math is wrong. If you change 25% of your water for four weeks only ~31% of the water is a month old.

100*.75*.75*.75*.75 = ~31

Back on the original topic: I change 25% weekly but by tank is small so that's only 5 gallons, for now.

 

[Shibaken3]

OK, a nice discussioin about the pros of water change. But my original post was asking, specifically, aquarist that for some reason or other eskew water changes or do them rarely. So unless those people really dont exist, Id like to know how that routine evolved (or devolved as the case may be). What observations, events, articles etc. lead you to stop doing water changes? I read "havent done a water change in 2 years", "no water changes going on 18 months, everything happy". Really? Why? Are you never going to do a water change?

I'm pretty sure lazy people that have easy coral gets away with no water change. I would like to see Acro thriving with no water change.

 

[Sump Crab]

I personally don’t water change on any schedule. I do about a 5 gallon water change every 4 or 5 months on my 65 gallon system. This is really because I’m lazy and the tank doesn’t seem to be negatively affected. I also do not dose anything at all. I do think my corals grow faster when I change more often. I’m

 

[newreef1]

There's not a lot of definitive data, but I generally recommend changing 1% daily is a decent plan. I did that on my system which varied from 250-350 gallons total volume. That is most readily dose with an AWC system. In my case, it changed water slowly and steadily, ~20 times a day, 24/7, 15 minutes of pumping each time.

That’s what @vetteguy53081 does. Lol but then it makes it so much easier, and if I’m not hauling buckets, pumps and spilling water everywhere did I even do a WC!?