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Is there any way to test for when to change water
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Josh Hansen

Joined: 20 Feb 2005
Location: Dayboro, Queensland, Australia

PostPosted: 2005.04.20(Wed)8:03    Post subject: Water change Reply with quote

I recommended 1/3 water change fortnightly or even once a week (if you want to make your water clean) and to do water test to keep the aquarium water quality under control. I used to do 50% of water change and found this situation a problem for a number of reasons it cause a few fish death from extreme changes in fish tanks water parameters from the added water , the chlorine, ammonia from the disinfection of the tap water being treated from the local council will increase and the unnecessary stress on the fish. I know at times you can do 50% waterchanges and not affect your fish but there will be certain unexpected times where you will have problems. Believe you me from my past experience you will one day have the problems coming from 50% water change.

from Josh
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Joined: 05 Dec 2004
Location: new york, ny

PostPosted: 2005.04.20(Wed)9:15    Post subject: Re: Water change Reply with quote

Josh Hansen wrote:
Believe you me from my past experience you will one day have the problems coming from 50% water change.
from Josh

I disagree. The assumption that underlies doing any water change is that the water chem is balanced enough not to cause stress. Obviously, in your case Josh, there are issues with the chem. caused by your bizare local water system. That said, changing 50% isn't uncommon. In fact, many discus folks change that much water daily or every other day.

ozziegt- I didn't mean to offend. I can see the point of confusion, but I think that the difference rested in the word thrive. If you were to do a 20 to 40% weekly, your fish would be fine. If you did more, then your fish would reap the benefits (again, this is assuming that the water chem is balanced/controlled enough not to cause issues).

Still, despite the articles that you posted, I think that the general consensus is that you should do 20% to 40% weekly or use your nitrates to gauge how often (which will probably work out to about the same time frame anyway, if not more often).
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Joined: 07 Feb 2003
Location: Ontario, Canada

PostPosted: 2005.04.20(Wed)9:36    Post subject: Reply with quote

Good discussion so far, lets stay calm about it everyone..
just so everyone can read why there are no exact answers on water changes you should know a few interesting factoids.

One, waste builds in a tank on a steady constant increase. Waste can be loosely monitored by measuring nitrates though this isn't true with live plants.
Water changes on a static pollution amount would follow a declining balance mathmatical formula where less is removed each time. Since the wastes are not a static volume, but an increasing level, this is not so. Instead, water changes acheive a balance of pollution content in your tank.
A healthy balance is directly proportional to waste added, vs. frequency and volume removed through changing water.

This balance is unique to each and every tank.

I have a 60g tank that I change 5g once every 3 months.
I have a 20g that needs 50% weekly.

So, in your discussions on this topic, it'll be best if you remember that there is no single answer for all tanks.

Hope that helps.
Discus Man is gone... I remain... #6... I am not a number I am a free man!
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Susan Wright

Joined: 09 Mar 2005
Location: Tulsa, Ok

PostPosted: 2005.04.20(Wed)9:56    Post subject: Reply with quote

I have to agree with Discus Man. My 75g I do a 30g change about once a month, and I still have to use AmQuel+ for the fact my tap water has nitrates of 120, this has been tested by me and by 3 different lfs. My 5 gal I do a 25% about every 3 days. It actually depends on how happy you want your fish to be. With my red tail shark, if I don't do my scheduled changes his red fin turns almost opaque, but as soon as I do the water change his is dark black and a very deep red fin.

He makes a good indicater I think. Razz
The critter ladie
8 cats, 2 dogs, 3 guinea pigs, FISH and more FISH
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Joined: 12 Jan 2005
Location: Tampa, FL

PostPosted: 2005.04.20(Wed)10:13    Post subject: Reply with quote


Sorry if my post caused confusion - it's just that since you mentioned live plants, I automatically assumed you would be doing the whole ferts/CO2/upgraded lighting deal. (Side note: Yes, for the poster who indicated that my 50% weekly water changes would be stressful to my fish, my tap water is nearly identical to my tank water after I dechlorinate it... even it's temperature, since I live in Florida. The only measurable difference is in nitrates. I'm bringing the nitrates from 30 to 15. If I was doing a large water change from really old dirty water, say, 300 ppm nitrates to 150, I'd agree that it would be stressful. But I'm doing large water changes on a regular basis to keep things at optimal levels. I've never heard research that doing that would be harmful to fish or plants. If you have some, I'd love to read it.)

You mentioned that you hadn't heard a good answer on when to change your water... the reason is that everybody's tank is different. Different sized tanks with different stocking levels are going to need different levels of care, as Discus Man illustrated with his two tanks.

Regardless though, I think most fishkeepers (aside from us plant freaks) use their nitrate measurements to guide water changes, and they change as much as necessary, as often as necessary, to keep their nitrates below 40 ppm. The timing and amount of the water changes are going to depend on your individual tank's parameters.

When I have more time, I will find the articles that I used to determine that the weekly 50% was right for my tank... but keep in mind, it's an aquascaped tank, with CO2, dosed ferts, and upgraded lighting. It's NOT the kind of tank Drs Foster and Smith are talking about.
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Joined: 07 Mar 2005

PostPosted: 2005.04.20(Wed)11:39    Post subject: Reply with quote

I tottally agree each tank is different, which is why I posted my question in the first place. Thanks for everyones answers. Smile
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