Why Should I Do Water Changes?

[rhostog]

My tap water from Anglian Water (MW38 zone) contains around 0.2 mg/L nitrite and somewhere between 20-50 mg/L nitrate. Currently my tank has a trace of nitrite, below 0.1 (I did a water change a few days ago and my relatively new tank seems to take an age to clear that last trace). My tank has around 10 mg/L nitrate - I've got quite a few plants and I'm assuming they're absorbing some of it. Ammonia is consistently zero.

I'm using the Nutrafin liquid tests, and it's hard to match the colours so my readings could be a little out, but I can say for sure that there is significantly more nitrite and nitrate in the tapwater than there is in my tank water - definitely the tap goes a much darker colour in the test tube for both tests.

It seems to me that I'm adding poisons every time I do a water change! OK, I need to clear waste off the substrate every now and then, and that means taking out some water, but is there any other benefit to changing the water? Are there any other chemicals accumulating in the water that get syphoned off? If I'm going to increase NO2 and NO3 every time I add fresh water, I'd like to know I'm doing it for a good reason!

Please don't think this is laziness - I've been very conscientious about water changes since getting the fish, and I'll happily continue if there's a good reason for it - I'm asking because I feel like I'm poisoning my fish .

 

[moll]

Well I know that my fry tank although it always has excellent readings if I don't change the water every 2 days or so the fry don't grow as fast as they release a hormone so I assume adult fish will need water changes for similar reasons.

 

[ALW]

A water change will also replenish any oxygen that the fish have used though breathing, As well as any other toxins that may be in the water.

 

[The-Wolf]

water changes are not just for diluting no3 etc
they are essential to replenish certain base elements and minerals that dissipate over time.

there is far more to water changes than changing H2O

 

[andywg]

A water change will also replenish any oxygen that the fish have used though breathing, As well as any other toxins that may be in the water.

I'm sorry?

Oxygen enters the water at the boundary with air, otherwise known as the surface. One does most definitely not need to do water changes to put oxygen back in the water.

Water changes are an easy way to keep the aquarium stable and avoid build ups of anything too nasty. It is certainly possibel to run systems that do not require water changes, though to make these work well they tend to take a lot of effort and invariably cost more than some dechlorinator will.

 

[OscarWilde]

If for no other reason, the fish seem to really the Waster changes in my tanks. It stirs up interesting things on the bottom and moves things around a bit.

 

[Miss Wiggle]

A water change will also replenish any oxygen that the fish have used though breathing, As well as any other toxins that may be in the water.

I'm sorry?

Oxygen enters the water at the boundary with air, otherwise known as the surface. One does most definitely not need to do water changes to put oxygen back in the water.

Water changes are an easy way to keep the aquarium stable and avoid build ups of anything too nasty. It is certainly possibel to run systems that do not require water changes, though to make these work well they tend to take a lot of effort and invariably cost more than some dechlorinator will.

although when you pour water back into the tank it will generally create a high amount of surface agitation which is after all the best way to increase oxygenation. Agree that it's not the point of water changes but increased oxygenation would be a side benefit..... for the short period immedatley after doing water changes.

plenty of people have trace amounts of ammonia and nitrite in their tap water and manage it quite fine. once the filter is mature it will happily process the little blip of extra nitrite just after a water change, while the tank's immature it may take a few days but eventually it'll get to the point where if you tested the tank an hr after a water change it'd be clear. a good way to help this is to do smaller water changes but more often, so instead of 30% once a week do 15% twice a week, so the overall amount of nitrite going into the tank at any one time is low.

as for nitrate, well don't even think about it, it's food for your plants and the quantity we're talking about will do no harm to fish whatsoever.

it would be more beneficial to do water changes to stop other toxins building up in the water

 

[andywg]

although when you pour water back into the tank it will generally create a high amount of surface agitation which is after all the best way to increase oxygenation. Agree that it's not the point of water changes but increased oxygenation would be a side benefit..... for the short period immedatley after doing water changes.

That would assume that your tank has such insufficient gas exchange that it is not already saturated with oxygen as it is (which for most of us is not true).

 

[Miss Wiggle]

although when you pour water back into the tank it will generally create a high amount of surface agitation which is after all the best way to increase oxygenation. Agree that it's not the point of water changes but increased oxygenation would be a side benefit..... for the short period immedatley after doing water changes.

That would assume that your tank has such insufficient gas exchange that it is not already saturated with oxygen as it is (which for most of us is not true).

and also assumes you don't just stick a hose pipe into the tank under the water level thus not creating surface agitation......

i was just being a little silly and facetious

 

[rhostog]

...
plenty of people have trace amounts of ammonia and nitrite in their tap water and manage it quite fine. once the filter is mature it will happily process the little blip of extra nitrite just after a water change, while the tank's immature it may take a few days but eventually it'll get to the point where if you tested the tank an hr after a water change it'd be clear. a good way to help this is to do smaller water changes but more often, so instead of 30% once a week do 15% twice a week, so the overall amount of nitrite going into the tank at any one time is low.

as for nitrate, well don't even think about it, it's food for your plants and the quantity we're talking about will do no harm to fish whatsoever.

it would be more beneficial to do water changes to stop other toxins building up in the water

Thanks - doing smaller water changes but more frequently makes sense to me, and I guess that's the way to go. I wasn't really considering leaving the tank as a closed system. It's just that everything I've read says we do water changes to lower nitrate levels, and if nitrites or ammonia start to build up, and I'm actually increasing these levels (only slightly, but still...) I've not read about other toxins or hormones building up, or minerals being depleted (apart from the need for plant fertiliser), but I'm new to all this and very grateful for the advice from more experienced people!

And my fish will be pleased - they seem to enjoy water changes - the danios swim around under the water being poured in, and the cories scuttle around collecting bits disturbed from the floor!

So thanks for the replies - 15% twice a week sounds manageable for the moment (I'll keep testing for a while yet), and see how I get on...

 

[ALW]

A water change will also replenish any oxygen that the fish have used though breathing, As well as any other toxins that may be in the water.

I'm sorry?

Oxygen enters the water at the boundary with air, otherwise known as the surface. One does most definitely not need to do water changes to put oxygen back in the water.

Water changes are an easy way to keep the aquarium stable and avoid build ups of anything too nasty. It is certainly possibel to run systems that do not require water changes, though to make these work well they tend to take a lot of effort and invariably cost more than some dechlorinator will.

Just becasue a small amount of oxygen enters the water at the surface doesnt mean that there is a sufficient amount within the tank, without it fish can suffocate. During the respiration process oxygen is used up and exchanged with co2. If a tank was left with fish an no water changes happened then they would eventually die of oxygen starvation. Sure aerators can do this on a small scale along with surface disturbance. Freshwater coming from a tap will have more oxygen within it than that coming from that tank (unless you directly put oxygen into the tank eg oxygen tablets). Water Changes put not only oxygen, minerials and metals back into the tank witch also will be used and depleted it also dilutes any harmfull toxins thst may be present within the tank.

 

[CFC]

A water change will also replenish any oxygen that the fish have used though breathing, As well as any other toxins that may be in the water.

I'm sorry?

Oxygen enters the water at the boundary with air, otherwise known as the surface. One does most definitely not need to do water changes to put oxygen back in the water.

Water changes are an easy way to keep the aquarium stable and avoid build ups of anything too nasty. It is certainly possibel to run systems that do not require water changes, though to make these work well they tend to take a lot of effort and invariably cost more than some dechlorinator will.

Just becasue a small amount of oxygen enters the water at the surface doesnt mean that there is a sufficient amount within the tank, without it fish can suffocate. During the respiration process oxygen is used up and exchanged with co2. If a tank was left with fish an no water changes happened then they would eventually die of oxygen starvation. Sure aerators can do this on a small scale along with surface disturbance. Freshwater coming from a tap will have more oxygen within it than that coming from that tank (unless you directly put oxygen into the tank eg oxygen tablets). Water Changes put not only oxygen, minerials and metals back into the tank witch also will be used and depleted it also dilutes any harmfull toxins thst may be present within the tank.

And where does that little pearl of wisdom come from then?

Gas exchange takes place at the surface, as movement caused by the filter disturbs the water CO2 leaves and Oxygen enters which is why planted tank enthusiasts try to get as little surface turbulence as possible otherwise all their added CO2 would be gassed away. For a tank to have anything less than optimum O2 levels it would need to be grossly over stocked and badly maintained or have no filtration running, and even then the movement of the fish themselves would generate some gas exchange. As long as water has movement and isn't full of rotting matter that sucks up Oxygen like a sponge it will remain well Oxygenated.

The point about minerals is true. A by-product of the nitrogen cycle is that humic acids are released into the water from the breakdown of organic matter. These acids eat away at the calcium carbonate (KH) that buffers the pH and unless replenished will eventually all be used up and the pH will crash.

Water changes have nothing to do with replacing Oxygen.

 

[ALW]

A water change will also replenish any oxygen that the fish have used though breathing, As well as any other toxins that may be in the water.

I'm sorry?

Oxygen enters the water at the boundary with air, otherwise known as the surface. One does most definitely not need to do water changes to put oxygen back in the water.

Water changes are an easy way to keep the aquarium stable and avoid build ups of anything too nasty. It is certainly possibel to run systems that do not require water changes, though to make these work well they tend to take a lot of effort and invariably cost more than some dechlorinator will.

Just becasue a small amount of oxygen enters the water at the surface doesnt mean that there is a sufficient amount within the tank, without it fish can suffocate. During the respiration process oxygen is used up and exchanged with co2. If a tank was left with fish an no water changes happened then they would eventually die of oxygen starvation. Sure aerators can do this on a small scale along with surface disturbance. Freshwater coming from a tap will have more oxygen within it than that coming from that tank (unless you directly put oxygen into the tank eg oxygen tablets). Water Changes put not only oxygen, minerials and metals back into the tank witch also will be used and depleted it also dilutes any harmfull toxins thst may be present within the tank.

And where does that little pearl of wisdom come from then?

Gas exchange takes place at the surface, as movement caused by the filter disturbs the water CO2 leaves and Oxygen enters which is why planted tank enthusiasts try to get as little surface turbulence as possible otherwise all their added CO2 would be gassed away. For a tank to have anything less than optimum O2 levels it would need to be grossly over stocked and badly maintained or have no filtration running, and even then the movement of the fish themselves would generate some gas exchange. As long as water has movement and isn't full of rotting matter that sucks up Oxygen like a sponge it will remain well Oxygenated.

The point about minerals is true. A by-product of the nitrogen cycle is that humic acids are released into the water from the breakdown of organic matter. These acids eat away at the calcium carbonate (KH) that buffers the pH and unless replenished will eventually all be used up and the pH will crash.

Water changes have nothing to do with replacing Oxygen.

I know a Oxygen isnt the main reason why we do a water change but it help to also know about it!

 

[andywg]

I know a Oxygen isnt the main reason why we do a water change but it help to also know about it!

It helps to stop saying water changes aid in putting oxygen back in the tank when the tank is continually doing so itself.

If you don't believe me, consider A post by Bignose on how an equilibrium is the desired state for nature/physics.

 

[Dorkhedeos]

Geez, its okay to be wrong. Just know when to admit it and stop so you dont look like a fool