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dragonhart
hi,

is 50% twice weekly Equivalent to 100% weekly? what are the pros and cons? thanks,
jason.
Hamad
Oh I'm curious too..anyone?
d_golem
80%-100% weekly:
Say the nitrate is 0 in day 1. It climbs to 40 in day 7. U change 80%-100% water, nitrate becomes 0-5 only.

50% twice weekly:
Say it's day 3, nitrate climbs to about 20, u change 50% water, nitrate become 10. Day 7 comes then nitrate already climbs to 30, then u change 50% again, nitrate only goes down to 15.

So which one u prefer? 5 nitrate or 15 nitrate? biggrin.gif

I hope my theory's right lol laugh.gif
gohks
QUOTE(dragonhart @ Thu, 06 Apr 2006 5:27 pm)
hi,

is 50% twice weekly Equivalent to 100% weekly? what are the pros and cons? thanks,
        jason.
*


Let me try answering this tough question. laugh.gif
Actually subjective as it depends on your load and your filtration efficiency to maintain good water quality. unsure.gif

50% twice weekly:-
Pros: Good in a way that water is renewed more frequently and any of contaminants or growth inhibitor your fish may see will be diluted. Infact, I will think 20% water change daily will be even better. Your fish will certainly grow better with this methodology.
Cons: More handling and maybe more stress to you and your fish. Also risk of fatality cause by mishandling is higher.

100% weekly:-
Pros: Totally new fresh water given, risk of left over is eliminated.
Cons: Fish needs to tahan for one week before water change. If you have a loaded tank with poor filtration and heavy feeding, this may post a problem. Also, fish needs to adapte to a totally new environment upon every water change. Water handling must be with great care to ensure we get back the original condition. On top of that, 100% water change is more taxing, water must be fully drained and top-up.

My preference is more regular water change. biggrin.gif
desireless
QUOTE(d_golem @ Thu, 06 Apr 2006 6:37 pm)
80%-100% weekly:
Say the nitrate is 0 in day 1. It climbs to 40 in day 7. U change 80%-100% water, nitrate becomes 0-5 only.
....
So which one u prefer? 5 nitrate or 15 nitrate? biggrin.gif

I hope my theory's right lol laugh.gif
*


This is a 9.5/10 answer good.gif

Nitrate is a good example to quote. Traces like nitrate will accumulate over the weeks if you do 50% twice weekly. So the alternative with better result is to do 100% weekly change, although the amount of water changed weekly is same for both cases.
Sabine
Things can be more complicated though. Many folks living in agricultural areas get the nitrates delivered with their tap water, some as high as 50ppm (the legal limit in many countries). Heavily planted tanks may be able to reduce the nitrates somewhat (if you keep a few tropicals only ;-)), but partial water changes will not cause the nitrate levels to go down much.
Water changes have to be very substantial then. Any other solutions for that problem? Nitrate filters? Do you have to deal with that problem in Singapore?
CP
d_golem's theory is right.Its all about nitrates management.Throughlly understand this link and you will get a clearer picture:
http://www.goldfishconnection.com/articles...d=67&parentId=8


In short,100% weekly is better than 50% twice a week.
And,50% twice a week is better than 20% daily.

To keep nitrates in check without growing linearly without limits, the minimum water change required, irrespective of the time frame, is 50%.That is to say that whether you change weekly,monthly or even yearly so long as your water changes are 50% or more, there is a maximum limit to the amount of nitrates that can be built up.

But,if you change 20% daily,the nitrate levels are going to build up continuosly without a maximum limit and that is bad.

Hard to believe?Pluck in some figures based on the link provided and you will get what I mean.
desireless
Hi Sabine,

The nitrate level in the Singaporean municipal water fresh from tap ranges from 0.5 to 15 ppm. It is unlikely that anyone in SG will get fresh tap water with anything more than that.

What you have raised is indeed a special situation.
dragonhart
thanks bro and sis for the replies,

i use to do 50% twice weekly(about 2-3 days in between WC) for a 4 feet tank(for the past 1 month) and 25% daily for a 2 feet tank. i just tried to do 100% weekly for the 4 feet tank.
i think need perhaps 1 month to see results.
long long ago LFS only recommend change 25% weekly and buy a big, expensive filter, no wonder my ranchus did not grow much.

cp and d_golem reinforced what i thought about water changes. Partial changes only dilutes the nitrates, let's say the tank has a nitrate reading of 40 ppm. A 100% WC reduces it to 0-5 ppm, changing WC 50% twice at one go(assuming no time for nitrate to accumulate) reduces it to 10 ppm(40/2= 20, 20/2 = 10).

btw my stocking is rather low...2-3pcs of 2.5 inch ranchu in 200L of water and i am only using two sponge filter.

so change 100% weekly but be very careful about adding of anti-chlorine and acclimatization to the new water.

QUOTE(dragonhart @ Thu, 06 Apr 2006 5:27 pm)
hi,

is 50% twice weekly Equivalent to 100% weekly? what are the pros and cons? thanks,
        jason.
*

dragonhart
good link CP, thanks,
jason.

QUOTE(CP @ Thu, 06 Apr 2006 9:41 pm)
d_golem's theory is right.Its all about nitrates management.Throughlly understand this link and you will get a clearer picture:
http://www.goldfishconnection.com/articles...d=67&parentId=8
In short,100% weekly is better than 50% twice a week.
And,50% twice a week is better than 20% daily.

To keep nitrates in check without growing linearly without limits, the minimum water change required, irrespective of the time frame, is 50%.That is to say that whether you change weekly,monthly or even yearly so long as your water changes are 50% or more, there is a maximum limit to the amount of nitrates that can be built up.

But,if you change 20% daily,the nitrate levels are going to build up continuosly without a maximum limit and that is bad.

Hard to believe?Pluck in some figures based on the link provided and you will get what I mean.
*

The Matrix
Keeping fish is never a constant number doing the +-/* ...

Even if the theory reinforce the idea of large water change, we could not ignore the fast climbing nitrogen waste products that created thru our feeding and other means. Even if one fix the duration and amount of change, one must also understand the feeding amount are never constant.

Fix the amount of at least 90%, probably going for the 100%, but the duration depends on the feeding. The more you feed, the shorter the duration. And that is also based on one assumption that the fish not big or overcrowded.

A lot of factor to consider but most importantly is observe the fish.
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