amosf
Aquarium Advice Regular
15ppm in a week? With one fish in a 450 litre tank? I don't get that in a 200 litre tank with 12 rainbow fish after a month. Even the goldfish aren't that bad...
Questions about water changes.
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BillD
Aquarium Advice Addict
One 7.5" Dovi is far more mass than 12 Rainbows, so, it eats more and evacuates more.
This is why I say it is irresposible for anyone to say arbitrarily that once a month is fine for water changes. The bioload in the tank determines what the minimum amount/frequency should be. Exceeding the minimum is better than running on the edge. If you have to miss a regular change, you are not likely to have problems. Personally, I wouldn't even bother to get the gear out for less than a 50% change.
This is why I say it is irresposible for anyone to say arbitrarily that once a month is fine for water changes. The bioload in the tank determines what the minimum amount/frequency should be. Exceeding the minimum is better than running on the edge. If you have to miss a regular change, you are not likely to have problems. Personally, I wouldn't even bother to get the gear out for less than a 50% change.
Agreed...
amosf
Aquarium Advice Regular
Hehe.. well monthly is hardly running on the edge for many tanks, certainly not in my experience, but everyone has their own opinion. I don't get readings like that on the goldfish tank, and it's bioload is way higher.
And nobody is saying that all tanks only need to be changed only once a month. What is being said here is more on the lines that all tanks need a weekly change, which is not always necessary. You can't over change water, so go for it. But in the end most tanks will be fine with a 50% monthly change.
Many years ago a tank would be likely to run a year or more without a water change, and while you would never see that today, and should not, the fish of the time survived in those conditions. I certainly had a tank like that 30+ years ago and kept fish for many years. In those days, with much less information available, there was a completely different school of thought with aged water and all he rest.
So 50% a month is well of the 'edge' by those standards
And I don't get nitrate readings in a month on any tanks, including the comets, for any tank that is close to the weekly reading mentioned here, which does seem odd to me.
I suppose I don't know the fish in question very well, or am confused by the measurements in cubits rather than standard metric
And nobody is saying that all tanks only need to be changed only once a month. What is being said here is more on the lines that all tanks need a weekly change, which is not always necessary. You can't over change water, so go for it. But in the end most tanks will be fine with a 50% monthly change.
Many years ago a tank would be likely to run a year or more without a water change, and while you would never see that today, and should not, the fish of the time survived in those conditions. I certainly had a tank like that 30+ years ago and kept fish for many years. In those days, with much less information available, there was a completely different school of thought with aged water and all he rest.
So 50% a month is well of the 'edge' by those standards
And I don't get nitrate readings in a month on any tanks, including the comets, for any tank that is close to the weekly reading mentioned here, which does seem odd to me.I suppose I don't know the fish in question very well, or am confused by the measurements in cubits rather than standard metric
BillD
Aquarium Advice Addict
So 50% a month is well of the 'edge' by those standards
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I'm curious to know exactly what type of nitrate readings you do get. The generally accepted high limit would be 40ppm. Half of that would be more appropriate, and half again would be better.
amosf
Aquarium Advice Regular
Lets see... after 2 weeks in the goldfish tank i test under 5mg/L in metric... which is same as ppm afaik. That's 200litre with 3 comets and 3 fantails, They would average about 100mm body length not counting tails.
That would be the heaviest tank load. Well maybe... The platy tank heavy as well... After a month it will still be under or at 5mg/L max.
That's an unplanted tank essentially - goldfish after all, tho they get plants cuttings thrown in there from the planted tank now and then. So some plants life in the tank on a casual basis. It is only lit about 5 hours/day anyway.
I'm always surprised by the nitrate readings I see in the forums at times. No way I ever see 20 mg/L much less 40 here.
If I went by what was said by some here, my nitrates would continue to climb. if they were 40 at the end of the month, a wc would bring it back only to 20. Another month it would be 60. After a few months it would be over 100.
Sometimes I do 75% wc, but still that would bring it down to only 10 from 40... So interesting how the figures differ so much.
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