View Full Version : At what point you say "its time for water change"?

09/19/2017, 08:24 PM
Im confused, and cant reside on when i should change water in my tank, I have a total of 430 gallons, its about 7 month old system, fish only. since the time i had it running i only did about 3 water changes of 10% during this period, and not because i had poor water testing results.
When do you guys change your water?

09/19/2017, 09:00 PM
You're prob going to get all kinds of opinions for water changes... consider your levels, research where they should be for what you have in the system, then do the math for how to export nutrient load, based on nutrient import.

Your particular answer will depend on your filtration and nutrient export methods... what levels should you be keeping for your livestock? Do you have an appropriate sized skimmer? Do you have a refugium? What is your bioload compared to size of tank? Not asking for answers, just posing things that should lead you to the answer you're looking for. :thumbsup:

ssgss gogeta
09/19/2017, 09:18 PM
For a Fowler it's going to be far less frequent provided your n and p stay in check. For a reef tank unless you are dosing to stabilize and maintain trace elements frequent water changes are more necessary. Each tank has different requirements and you just have to play trial and error.

In saying that there are many successful tanks that survive and flourish with either minimal or no water changes but they dose and export nutrients on much greater levels than the average tank

Sent from my iPhone using Tapatalk

09/19/2017, 09:20 PM
thank you for reply. but i will answer those questions. i have 150g sump, in it i have: 6 socks, rated for 700g skimmer, refugium with 150 mangrove stems. 3200gph return pump. in main tank i have about 170lb of dry rock and 25lb of live rock from established tank. my nitrate never goes over 5-10 ppm, using redsea and api test kit

09/20/2017, 12:45 AM
I do water changes just to suck out detritus that builds up around the bottom of my tank, or around the edges of my rockwork. It takes a month or two for it to bother me enough to do it. Infact I have always found that when i keep my hands out of the tank things always look better. So I kind of, sort of, try and avoid water changes.
If any corals start looking ****ed then i might to 10 gallons. My total water volume is around 220gal.

on the spot
09/20/2017, 06:58 AM
...when i should change water in my tank, I have a total of 430 gallons...fish only...

...my nitrate never goes over 5-10 ppm...

you could go a long time without really noticing a difference.

and mangroves. groovy.


btw, 6 socks seems like a maintenance headache. why so many @ a time?

09/20/2017, 02:04 PM
Water changes are not just about nitrate/phosphate reduction..

The remove other dissolved organics, attempt to replenish trace elements, maintain cal/alk/mag levels,etc....

In general the solution to pollution is dilution and water changes do that..
Over time things may build up in our tanks (much we can't/don't test for)..
So a big chuck of water changes is a gut feeling/watching your corals,etc...

If everything seems to be doing fine and levels that you do test for are good then you can look into reducing the amount or frequency.. Just watch/test/adapt as needed..

09/20/2017, 05:11 PM
I agree with mcgyvr. I think of this as analogous to lifestyle choices. Maybe you go to the gym twice a week. You don't typically go to the gym because something is wrong. You go because years from now you want to have better health.

My current routine is a 10% change every other week. I have done more and less, sometimes much less, but this is what I'm doing now. The frequency correlates well with my interest level, which has waxed and wained over the years.

09/21/2017, 06:56 PM
. . . They remove other dissolved organics . . .

~+1 :D

Corals and algae release a myriad of DOC (Dissolved Organic Compounds), Some is recycled by cryptic sponges into stuff that is used by other organisms (including conversion back to inorganic nitrogen and inorganic phosphate [aka PO4]) but refractory types of DOC build up in the aquarium. The only way to get rid of refractory DOC is with water changes. Waiting until there's an obvious problem is waiting too long.

09/22/2017, 11:35 AM
I find that establishing a routine helps keep thing steady. In my case I have a 60g hex and do a weekly 5g WC (one bucket), with reasonable success 3 years and counting.
In your case you will scale up the volume of WC but establish your own schedule that you can stick to. BTW, you still have a 7 month young tank . . . It is still maturing . . .