View Full Version : Max. % water change
mystic1
06-07-2007, 8:31 AM
What is the largest % water change that can be done at one time with the least adverse effect on the fish?
J double R
06-07-2007, 8:39 AM
any particular fish in mind? or just in general?
mystic1
06-07-2007, 8:52 AM
It is the temp. tank for a Severum, geophagus and a ctenopoma leopard. I normally do smaller more frequent water changes but for the next 3 weeks I will only have 2 opportunities to do water changes.
is the Ph in the tap significantly different from the Ph in the tank ? That would be my main concern - possibility of shock if you did like a 75% water change or more.
star_rider
06-07-2007, 10:35 AM
I have actually seen a 90+% water change in a larger discus tank.
Nolapete
06-07-2007, 10:51 AM
Think about acclimating fish. You shouldn't add enough water at one time to make the water they are used to only 10%, so why would you do that in your tank? The most I'd say without causing undue stress would be 50%, but that's pushing it and should be for emergencies only. If you can do two over the course of 3 weeks, I'd suggest 40% per water change.
week 1 normal 25%
week 2 normal 25%
week 3 normal 25%
total 75%
wc 1 40%
wc 2 40%
total 80%
That way you are covering your weekly 25% then an additional 15% for the first half of the following week that you can't do. Then when you do the next one you're doing 10%+5% to make up for the missed one and then 25% for the normal one.
Mgamer20o0
06-07-2007, 11:10 AM
i like large water changes are 50-75% if not more. i have done 80-90% water changes with no problem before.
star_rider
06-07-2007, 11:16 AM
large water changes will not hurt the fish or cause undue stress..you need to get the water params close. temp within a few degrees and if you are using tap as your source you won't be adding a dramatically different water.
if you are using ro/di and using buffers..24 hrs prior to a large water change set up your holding tanks to accomadate a large change.
like Mgamer I have don large water change 50-75 % I do 40-50% 2 X week in most of my tanks.
keep in mind wild fish may see larger dramatic swings during the rainy season and not suffer mcuh stress.
mostlycichlids
06-07-2007, 11:19 AM
Larger water changes are fine and the fish will only benefit from nice pristine clean water. I have been doing 30-50% weekly water changes on most of my tanks for years. My fish are so happy when the filters kick back on and the tank is full and clean. If you have high Nitrates then 25% weekly wont do much. It really depends on the Nitrate levels if after a week you are still under 10 ppm then 25% should be fine. I have a couple of tanks that I change 3 times a month at 50% every 10 days. This is because I have excellent filtration and low Nitrates. None of my tanks ever get polluted over 15ppm.
Nolapete
06-07-2007, 1:00 PM
If your nitrates are going up way high between weekly 25% water changes, you are most likely overstocked or overfeeding.
mystic1
06-07-2007, 1:56 PM
Thank you guys for the info. I feel more confident now that everything will be fine.
mostlycichlids
06-07-2007, 10:26 PM
If your nitrates are going up way high between weekly 25% water changes, you are most likely overstocked or overfeeding.
You could also be underfiltered!
star_rider
06-07-2007, 10:42 PM
test the source water. many times you may already have nitrates ..my source water (tap) can read as high as 20ppm
I personally only use the nitrate count as a gauge..and in a planted tank it doesn't work as a gauge. as the nitrates count is adversely affected by the plants and is not a reliable indicator of TDS..which in reality is what we are actually trying to reduce.
this is not to say that high nitrates don't adversely affect the fish as they can cause issues over a prolonged exposure.
remember that nitrates are a by product of the bacteria that are consuming the nitrites.
in a large tank with a sump (high fitration) you can have a nigh nitrate count due to residue that reamins in the bio media..what this indicates is..the bio media needs to be rinsed occassionally to remove these unwanted materials.(rinse in tank water)
the same can be said of cannisters and HOB. the I usually only rinse abbout half at anyone time.bio media does need to be rinsed every once in awhile..to remove this mulm.
rbishop
06-08-2007, 5:44 AM
The bigger the better. The more frequent the better.
rbishop & anyone else, for my own information, if I decided to do say a 90% water change should it concern me that my tap Ph is 7 and in the tank its buffered to 7.8 ? Seems like quite a swing very quickly.
mostlycichlids
06-12-2007, 9:08 PM
rbishop & anyone else, for my own information, if I decided to do say a 90% water change should it concern me that my tap Ph is 7 and in the tank its buffered to 7.8 ? Seems like quite a swing very quickly.
it really depends what you are buffering with and if you are adding anything to the tap water to match your ph in the tank. I have a 7.2 ph out of my tap and do 50% weekly water changes on my 75g weekly. I have been doing this for a while so I know how much buffer to add to match the PH. Never had a problem in a few years now.
Weezer
06-12-2007, 9:14 PM
I guess I'm fortunate that the tap and the tank are in the mid 7's, I do 2 50% changes a week..........
mostlycichlids
06-13-2007, 12:09 AM
it really depends what you are buffering with and if you are adding anything to the tap water to match your ph in the tank. I have a 7.2 ph out of my tap and do 50% weekly water changes on my 75g weekly. I have been doing this for a while so I know how much buffer to add to match the PH. Never had a problem in a few years now.
I forgot to add that the PH in the tank stays at 8.0
When I do a water change, I don't pre-treat the water. The tap water is 7.8 for me and my main concern is temp shift during a water change.
I have a 3rd heater that gets switched on during water changes, but this is bizarre:
The fish appear to LIKE the cold water that trickles into the tank.. in fact they get right in amongst it :headshake2:
I found this was the case with new worlds when I kept them and they suffered no ill effect, and appeared to enjoy it!
In terms of those high volumes you mention, I have had to do something like this when moving house, and there have been no ill effects at all. I was concerned with fiddling with the PH initially, but the benefits appear to completely outweigh the concerns. Perhaps a slower water change will be enough.
I don't actually know how long PH takes to adjust regarding substrate etc in the tank..
rbishop
06-13-2007, 8:11 PM
rbishop & anyone else, for my own information, if I decided to do say a 90% water change should it concern me that my tap Ph is 7 and in the tank its buffered to 7.8 ? Seems like quite a swing very quickly.
Guess it would depend on how you are buffering. I'm not sure that many run of the mill hobbists do, except by some bottled chemical means and probably not for the reasons an aquarist would be doing it.
I would think that if I had a tank with special water needs, I would have water ready to do it at the correct pH, temp, GH/KH. And enough to do a 90% change.
My comment was about water changes in general, the bigger the better and the more frequent, the better. I never stated to add big water changes frequently with water that did not match your tank conditions.
Mgamer20o0
06-13-2007, 9:07 PM
having water ready to go is a very smart idea like RB said.
Guess it would depend on how you are buffering. I'm not sure that many run of the mill hobbists do, except by some bottled chemical means and probably not for the reasons an aquarist would be doing it.
I would think that if I had a tank with special water needs, I would have water ready to do it at the correct pH, temp, GH/KH. And enough to do a 90% change.
My comment was about water changes in general, the bigger the better and the more frequent, the better. I never stated to add big water changes frequently with water that did not match your tank conditions.
understood (re the last part)I've since checked my Ph swing on doing a large water change and it is minimal in any event - couple of points down, maybe not even that.
rbishop
06-14-2007, 5:09 AM
That's a good thing to know. Anybody keeping fish requiring specific water needs other than straight tap, shoul know what a full tap water change will do to their tank.
star_rider
06-14-2007, 5:51 PM
rbishop & anyone else, for my own information, if I decided to do say a 90% water change should it concern me that my tap Ph is 7 and in the tank its buffered to 7.8 ? Seems like quite a swing very quickly.
if you are doing large water changes ad frequent changes..you may want to consider using a large storage container. fill with water, buffer add heater and small powerhead..use as needed.
I have marine tanks..I use ro/di for these and use the synthetic salt mixed to get the water to the right ph, SG kh
I pump ro/di to a large 60 gallon tank that has a heater and circulation pump/powerhead.
I drain what I need to a smaller 30 gallon tank for mixing add mix to get SG to 1.024.heat and circulate for several hours up to 24 hrs..then retest water and use for water changes.
it is a method that a local discus breeder uses too''only on a much larger scale he has a 1000 g holding tank and mixing water (total)