big water change

[Weyou]

I am thinking of doing a big water change in my aquarium, around 60 percent. Aquarium has been active for over two years but is not happy with its results for all sorts of reasons. I know this is not a long term solution but worth a try. My big fear is that it will stress my fish and corals. By the way I do not have hard corals

 

[blaxsun]

Why not do two 30% changes instead, separated by a week or two?

 

[Weyou]

Why not do two 30% changes instead, separated by a week or two?

Because I saw a YouTube video demonstrating a scientific experiment that dilutes nitrate and phosphate, water replacements that are less than 50 percent are not particularly effective.

 

[blaxsun]

I can't comment on said video, but larger water changes will always be more stressful. If the concern is high nitrates and phosphates, a lot of this can get locked in the rocks - and a large water change won't necessarily provide relief.

So without knowing a bit more about the issues (and parameters), it's hard to offer an opinion whether a single 60% water change will do the trick. I suspect it might only scratch the underlying problems.

 

[PatW]

Two 30% changes will decrease nitrate by 49% (.7 x .7) and a 60% change will decrease it by 60%.

For large changes, you want the ALK, salinity and temperature to match the aquariums. Otherwise you should be good.

 

[atomos]

I'm not a big fan of big water changes at once. I prefer the method that others recommended. Alternatively, I like to use Hamza's calculator for water changes to get a good guesstimate of things (like reducing nitrates)---

Effect of Water Changes Calculator

Aquarium calculator; Estimate the effect of repeated water changes on the concentration of a given substance.

www.hamzasreef.com

 

[Super Fly]

if stress to livestock is concern, I'd do several 30-40% water changes 1-2 days apart until the desired parameters are reached instead of a week apart.

 

[socalfishy]

If i need to do a big water change, i always get another heater and prepare the water so that the temperature shock is less stressful. Really big changes and drastic temp differences are not good.