Can someone please explain the science behind 75% water changes
75% water changes
- Thread starter itiwhetu
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Solution to pollution is dilution. Thats what everyone says around here. If you have 1 ppm nitrates in your tap, and 40 ppm in your tank, if you take out more than you add in, thus resulting in less toxic water and a less stressful environment. It works for nitrite, ammonia, ich and anything negative in your tank water. Or so I've heard
.
More water removed, more waste remove, more fresher replenished water added back to a closed system.
There are things in our tank water we don't test for, most of which are removed with water changes.
You cannot have too much clean water
There are things in our tank water we don't test for, most of which are removed with water changes.
You cannot have too much clean water
Also;
Tank water parameters drift over time, away from the conditions of the source water you use during water changes, and in lots of ways that we don't even measure. Leaving a tank for a long time without many water changes, or worse, only topping it up for months or years, means the chemistry has changed a lot from your tap water. pH is one quality that drifts in tanks, but there are others.
Now imagine an emergency happens. Your tank breaks, a toddler tips a whole pot of fish food into the tank, an outbreak of disease requiring daily water changes, etc etc... and 100% water changes are now essential. Now, doing a huge water change will be a big shock to your fish, who have acclimated to the sky high nitrates, drifted pH, and many other aspects of the old water chemistry, and they're plunged into water that is now very different in a whole bunch of aspects of its chemistry. The shock can be big enough to kill the fish, and it's one reason old school fish keepers were so scared of water changes.
Doing large weekly changes keeps your tank water parameters close to your source water chemistry. Allows you to keep the tank stable, because an established tank filtration already handles ammonia and nitrites through the nitrifying bacteria that live in the filter and on every surface, not in the water column itself. The other aspects of the water chemistry, you want to be as close to your source water as possible, which you can do by refreshing the water through large regular changes.
Look up "old tank syndrome" if you wish to learn more.
Also look up why clean fresh water is the best medicine for fish that are struggling with, well, anything. Reduces bacteria, fungal spores and parasites that are in the tank water, keeps ammonia/nitrites/nitrites low, and allows the fishes immune system to battle the illness more easily.
Tank water parameters drift over time, away from the conditions of the source water you use during water changes, and in lots of ways that we don't even measure. Leaving a tank for a long time without many water changes, or worse, only topping it up for months or years, means the chemistry has changed a lot from your tap water. pH is one quality that drifts in tanks, but there are others.
Now imagine an emergency happens. Your tank breaks, a toddler tips a whole pot of fish food into the tank, an outbreak of disease requiring daily water changes, etc etc... and 100% water changes are now essential. Now, doing a huge water change will be a big shock to your fish, who have acclimated to the sky high nitrates, drifted pH, and many other aspects of the old water chemistry, and they're plunged into water that is now very different in a whole bunch of aspects of its chemistry. The shock can be big enough to kill the fish, and it's one reason old school fish keepers were so scared of water changes.
Doing large weekly changes keeps your tank water parameters close to your source water chemistry. Allows you to keep the tank stable, because an established tank filtration already handles ammonia and nitrites through the nitrifying bacteria that live in the filter and on every surface, not in the water column itself. The other aspects of the water chemistry, you want to be as close to your source water as possible, which you can do by refreshing the water through large regular changes.
Look up "old tank syndrome" if you wish to learn more.
Also look up why clean fresh water is the best medicine for fish that are struggling with, well, anything. Reduces bacteria, fungal spores and parasites that are in the tank water, keeps ammonia/nitrites/nitrites low, and allows the fishes immune system to battle the illness more easily.
OP
OP
If you do a 75% water change doesn't that defeat the purpose of cycling a tank
No, because nitrifying bacteria live primarily, if not solely in the filter and substrate. There is none in the water.
OP
OP
I was always taught a little often.
The old school method for fish keeping said to do a 10% water change each week. Unfortunately this leaves a lot of nasty stuff behind. These days bigger water changes are recommended because they dilute things more effectively.
People do water changes to reduce nitrates and chemicals released by fish, but there is another reason to do water changes. Fish live in a soup of microscopic organisms including bacteria, fungus, viruses, protozoans, worms, flukes and various other things that make your skin crawl. Doing a big water change and gravel cleaning the substrate on a regular basis will dilute these organisms and reduce their numbers in the water, thus making it a safer and healthier environment for the fish.
If you do a 25% water change each week you leave behind 75% of the bad stuff in the water.
If you do a 50% water change each week you leave behind 50% of the bad stuff in the water.
If you do a 75% water change each week you leave behind 25% of the bad stuff in the water.
Fish live in their own waste. Their tank and filter is full of fish poop. The water they breath is filtered through fish poop. Cleaning filters, gravel and doing big regular water changes, removes a lot of this poop and makes the environment cleaner and healthier for the fish.
People do water changes to reduce nitrates and chemicals released by fish, but there is another reason to do water changes. Fish live in a soup of microscopic organisms including bacteria, fungus, viruses, protozoans, worms, flukes and various other things that make your skin crawl. Doing a big water change and gravel cleaning the substrate on a regular basis will dilute these organisms and reduce their numbers in the water, thus making it a safer and healthier environment for the fish.
If you do a 25% water change each week you leave behind 75% of the bad stuff in the water.
If you do a 50% water change each week you leave behind 50% of the bad stuff in the water.
If you do a 75% water change each week you leave behind 25% of the bad stuff in the water.
Fish live in their own waste. Their tank and filter is full of fish poop. The water they breath is filtered through fish poop. Cleaning filters, gravel and doing big regular water changes, removes a lot of this poop and makes the environment cleaner and healthier for the fish.
OP
OP
If you remove all the bad stuff you must also be removing a portion of the good stuff as well. How does the bacteria in the filter cope with a huge shift in water quality especially if it comes off a town supply
Metalhead88
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The good stuff mostly lives on surfaces. Not in your water.
OP
OP
So how does a 75% water change effect that bacteria
It doesn't.
Most of the harmful stuff lives in the water and on/ in fish poop.
Most of the good bacteria live on hard surfaces.
As long as the new water is similar in pH, GH and temperature to the tank water, there is no detrimental effect to the fish, plants, good bacteria or anything else in the tank.
The GH and pH from your water supply does not normally change, so unless you change your water source, there is unlikely to be a difference.
Most of the good bacteria live on hard surfaces.
As long as the new water is similar in pH, GH and temperature to the tank water, there is no detrimental effect to the fish, plants, good bacteria or anything else in the tank.
The GH and pH from your water supply does not normally change, so unless you change your water source, there is unlikely to be a difference.
Last edited:
OP
OP
Got it, I have only done 75% water changes on fish tanks in an importers establishment where we were using high doses of chemicals, and have never heard of it being done in home aquariums on a regular basis. Always willing to learn new stuff about this hobby
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