What's more effective. Frequent smaller water changes or single huge ones?

RD.

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This is exactly why I always stress that one size does not fit all in this hobby, especially when water changes are considered. I know my water parameters intimately, as I do my fish, so massive water changes, even in the 90% range are never an issue. Having said that, I would never suggest that is something that the next hobbyist should be doing.
 

Lepisosteus

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Algae consumes nitrates as well as an array of other nutrients. As algae starts to grow nitrates/nutrients will decrease unless you increase input. You can have a low nutrient system on a test kit and still have lots of algae in your tank because all the nutrients are being used by the algae. It’s all a balancing act. If you want no algae, remove all algae from glass, rock, etc and maintain low nutrient levels following the removal.
 
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FINWIN

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As a follow up, I've tweaked the water change volume in the 225. It's still twice a week.

Current stocking:

11" Oscar (at last measurement)
~ 6-7" Severum
~6-7" Blood Parrot
7" Ocelllifer Syno cat
6" Eupterus Syno cat

Standard w/c volume was 50% and increased to 60% once the cichlids put on more size and bulk. Oscar was measuring stick used, once he passed 10".

Tested up to 80% w/c but synos got stressed from it consistently, flashing and swimming erratically for hours

Backed off to 70% -75% max volume and no problems

On the (2 ) 38 gallon , stocking for each tank:

1 7" blood parrot
1 ~6-7" blood parrot

Added larger pothos with thicker root systems, (2 )20% w/c per week
mechanical filtration muck greatly reduced

For the female parrot 3 water changes a week when she lays eggs. Protein buildup is rapid from her huge egg production creating foam and 'thick' water. Less buildup in her mechanical filtration since she will refuse food until done, usually 3-4 days.

These are the current adjustments.
 

Tj203

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Think both are effective. Depends on bioload. Think the small and frequent water changes keep some stability with the water. Not much swings with ph and Gh.
I agree if your nitrates are high you need to do a big one to get them down but if you are on top of your maintenance i think i would be better to do smaller water changes because the swing in the ph , gh . i try and keep my water around 7.8 my tap is around 7.0 thats why i do small ones
 
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Rocksor

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I agree if your nitrates are high you need to do a big one to get them down but if you are on top of your maintenance i think i would be better to do smaller water changes because the swing in the ph , gh . i try and keep my water around 7.8 my tap is around 7.0 thats why i do small ones
What's causing your PH to go up? The substrate?
 

RD.

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I don't have swings in pH, or GH. Ever. 80-90% water changes. Not all tap water, or tank set ups, are going to be the same when you are dealing with such a wide spectrum of fish keepers.
 
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duanes

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I don't have swings in pH, or GH. Ever. 80-90% water changes. Not all tap water, or tank set ups, are going to be the same when you are dealing with such a wide spectrum of fish keepers.
I agree with this, for me a 30-40% water change every other day was adequate to keep nitrate low, and pH stable.
What I did was keep a log book of water parameters, watched the trend, and the trend told me what worked best.

I hardly ever over stocked tanks, usually only 3 to 5 fish every 100 gallons.
On over stocked, and overly fed fry tanks sometimes more water changes were needed, to promote growth and better water quality.
It all depends on how to stock, how many gallons, and your perceived nutrient load goal.
My nitrate goal is always this.
fullsizeoutput_1280.jpeg
Each aquarist needs to assess and decide their own attitude to semi-toxic substances.
 

islandguy11

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Regarding semi-toxic substances -- I've read a couple of places that nitrate doesn't actually become toxic to fish unless nitrite is also present -- is this true or false? (I have no idea).

In my 4 tanks (total ~1,150 gallons) I personally aim to keep nitrates about 15ppm, max 20ppm, which I can accomplish with ~50% water changes once a week on 3 tanks (the 4th is a 375 with just 2 fish (8" & 10") and can easily go 2 weeks and still be about 15ppm).

No doubt my fish would be even better off if I could get nitrates down to 5-10ppm, but with ~8ppm already in my tap water getting them too much lower than 15ppm wouldn't be easy, unless perhaps I brought plants into the equation or utilized some kind of auto-water change system (possible in future but not practical at this time).
 
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ad88

Candiru
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I agree with this, for me a 30-40% water change every other day was adequate to keep nitrate low, and pH stable.
What I did was keep a log book of water parameters, watched the trend, and the trend told me what worked best.

I hardly ever over stocked tanks, usually only 3 to 5 fish every 100 gallons.
On over stocked, and overly fed fry tanks sometimes more water changes were needed, to promote growth and better water quality.
It all depends on how to stock, how many gallons, and your perceived nutrient load goal.
My nitrate goal is always this.
View attachment 1388720
Each aquarist needs to assess and decide their own attitude to semi-toxic substances.
Are you gravel vacuuming every time you do a water change?
 

Ulu

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On over stocked, and overly fed fry tanks sometimes more water changes were needed, to promote growth and better water quality.
My bare-bottom brackish fry tank gets siphoned every day now, and 50% water change.
I have algae growing and the fish are eating a lot and growing fast.
Plus they get flake food 3x a day.
I've never bred guppies and mollies in brackish water before and never had this success.
Or this much feces!

I have never "freshened" the fry tanks enough in the past.
 
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