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

FINWIN

Dovii
Original poster
MFK Member
Dec 21, 2018
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There are many species of algae, when I was doing microbiology studies I had a text book dedicated solely to the algal species the Great Lakes.
There are over 800 species of Euglena algae alone.
Some such as cyanobacteria,(are really not, but thought of as algae),thrive in nutrient rich (polluted) environments, and some in what would be considered non-polluted ones, and there are those species that thrive more according to light intensity, than nutrient but "all" will use nutrients, and those available nutrients seem to dictate which algal species thrive, so not really conflicting, just many types, desired and undesired by the aquarist.
It's all about balance in aquariums, if a balance is off, you may get unwanted Cyanobacteria (slime algae).

Above a tank of mine that got an intensity of light that produced slime algae, I needed to encourage different microorganisms to compete with it, to lose it.
In a well balanced system, you may get a desired species, below

In the Cenote below, there were Molly species that reached outrageous sizes of over 7", eating algae (almost exclusively)

These Cenotes were nutrient poor (no detectable nitrate), but received intense sunlight.
At the moment, I am running an algae scrubber type sump(it sits in direct sun), the algae in the sumps thick, but hardly any in the tank proper, smite I believe, by the heavy higher plants and light fish load, in comparison.
So far the tank water, has had undetectable nitrate.
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When some algae gets too thick in the sump, I rip some out, and feed it to the cichlids.
View attachment 1383675
Interesting! Had no idea there were so many varieties of algae type organisms.
 

RemainVayne

Plecostomus
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Sep 26, 2017
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I would be curious how large, frequent water changes factually compare to drip systems. I do 75% changes 2x/week on my 150 and have a 4gph drip setup on my 360g (480g total with sumps). The drip equates to a total of 672 gallons a week, but we all know that drips don't take out only old water. The drip line is placed into the input guard on one of my pumps to encourage the new water to get sucked right into the tank and the drain line is in the last compartment of my sump.

I don't frequently take numbers on the drip tank, but it shows less than 10ppm nitrates when I do. The tank is heavily stocked and fed quite heavy too. However, the fish have shown tremendous growth and improved appearance after being moved from the 150g.

Just more to add to the discussion...
 

fishhead0103666

Redtail Catfish
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May 14, 2018
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I will put in my opinion. I personally believe that large water changes are the way to go and my reasoning is that you'll have to change out a higher volume of water with samller water changes to equal the amount of water changed with larger water cahnges. This not only means you spend more time but you also use more water and more chemicals to treat the water (if you must treat it).
If anyone wishes to see the math behind my logic then I will show it.
 

Mr Pleco

Piranha
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Mar 18, 2006
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Not going to challenge your math skills , I believed in large water changes too . However I'm on city water from a river and the charactisitics of my tap water changes with the seasons . Ive had too many scares and lost fish from doing 50%+ wc 's ... I prefer the drip method uses more water but my fish are not stressed , and growing like weeds.
 

piranhaman00

Aimara
MFK Member
Sep 15, 2009
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I will put in my opinion. I personally believe that large water changes are the way to go and my reasoning is that you'll have to change out a higher volume of water with samller water changes to equal the amount of water changed with larger water cahnges. This not only means you spend more time but you also use more water and more chemicals to treat the water (if you must treat it).
If anyone wishes to see the math behind my logic then I will show it.
These points are exactly why you should not do large water changes. If you are meticulous, sure you can do single large water changes, but your parameters ( pH, dKH, salinity ect ) better be matched up very accurately. You also have to add greater amounts of chemicals to the water system at once. Yes they equal in the end but smaller amounts over time do not expose the aquarium to large amounts at once.

Frequent water changes also keep nutrient levels in check with out drastically fluctuating from high to almost 0.

Large w/c definitely work but I think more care has to be involved and more sensitive fish could suffer from them.
 

LBDave

Peacock Bass
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Nov 27, 2018
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I see more growth with frequent large water changes. I also clean the substrate each time. Every 3 to 4 days. For large cichlids and cichla I am a firm believer in this for growth and disease prevention.
But that's me and what I do.
 
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Rocksor

Blue Tier VIP
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Nov 28, 2011
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I will put in my opinion. I personally believe that large water changes are the way to go and my reasoning is that you'll have to change out a higher volume of water with samller water changes to equal the amount of water changed with larger water cahnges. This not only means you spend more time but you also use more water and more chemicals to treat the water (if you must treat it).
If anyone wishes to see the math behind my logic then I will show it.
Does the math take into account waste or detritus matter removed by substrate vacuuming every time a smaller water change is done?
 

fishhead0103666

Redtail Catfish
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May 14, 2018
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Does the math take into account waste or detritus matter removed by substrate vacuuming every time a smaller water change is done?
The math focuses solely on the ratio of new water to old water with each watch change.

Just as I was typing “I do not believe it matters either way” I realized something. If you were to do one single water change then the detritus builds up over the week while if you do smaller water changes the levels don’t get the chance to rise up very high.
Thank you rocksor for bringing that up.
Going off of that information perhaps it would be better to do a large water change at the end of the week and a small water change strictly for cleaning the substrate halfway through the week?
 
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