How Many water changes?

[oogie]

I have very high nitrate.

How many water changes will it take to lower it/?

 

And how often?

 

Thanks

[MKramer]

The math here is pretty simple.  Changing 25% of your water will reduce the nitrate 25%, as it is fairly evenly distributed about your water.

 

Without knowing exactly what the nitrate level is, I'm assuming that it's quite high.  In which case, you'd need to replace a considerable amount of water.  Doing big water changes is detrimental to your tank's inhabitants (including the bacteria colonies that process your ammonia, nitrite, and nitrate), so you'll have to do it in stages.  I'd recommend no more than 15%, every other day.

 

Again, I don't know your actual levels, but I would wager than only 2 or 3 such changes would be needed to bring nitrates back down to undetectable levels.

[Sahin]

I agree.  Carry out no more than 15% change every other day.  Else you'll likely create too much of water parameter fluctuation which itself is worse than the high nitrates.

 

Gradual water changes is the best way to go.

 

I am assuming this is a fresh tank.  Else if its an established tank you would need to consider whats causing high nitrates.  An estalished tank should have no more than 5ppm nitrates and ZERO at best if possible.

[oogie]

Yes I am in the process of cycling.

Does nitrate also spike and fall down or just ammonia and nitite do that?

 

Thanks

[MKramer]

In a nano-reef, nitrate will not decrease on its own.  So there is no spike and fall, just a gradual build-up.  

 

In larger aquariums, with massive amounts of liverock and a deep sand bed, there is a large enough population of anaerobic bacteria that aid in eliminating nitrates.  Because we lack that luxury in a nano, the most effective way to eliminate nitrate is manual removal (ie, water changes).  That is why a weekly or biweekly water change is one of the mandatory "tricks" for keeping a nano-reef alive.

 

Matthew

[Leonard]

I respectfully disagree with small water changes.  It's a simple issue of dilution, and small volume changes isn't going to accomplish much unless you're committed to doing many (and I mean many) of them.

 

Here's an example: You take 15% of 10 gallons with NO3 level of 100ppm, and you'll (theoritically) remove 15ppm of nitrate.  Next water change, take 15% of 85, and you remove only 12.75.  Take 15% of 72.25 on the next change, and you're only removing 10.83 this time.  And so on ....

 

Small water changes become less and less effectual over time.  

 

I'd much rather do one large water change so long as salinity and temperature are matched well.  Osmoregulation is the number one concern when doing water changes.  

 

To dillute high nitrate levels, I'd do a single or tandem of 50% volume water changes.  I can tell you from experience that matched properly, you'll observe no negative responses from any of your inhabitants.  I wouldn't worry too much about aerobic bacteria, as they are EXTREMELY hardy and resistant to all but the most severe physical and chemical changes.

 

Another good way to alleviate nitrate levels is to employ macro-algae and/or activated carbon/polyfilter (or anything that readily absorbs DOCs).  Skimmers are a nice option if you can fit one and afford one.

 

(Edited by Leonard at 7:14 pm on June 18, 2002)

[flaunt]

Leonard has a good point about the small water changes decreasing in effectiveness.. in actuality though (if you start with 100ppm) you might be removing 15ppm with the first water change, but the next water change probably wouldn't be just 15% of 85, it could be more like 15% of 90 or so... it all depends on what's going on in your aquarium.  if you do have a continual buildup of nitrate then i would go with some type of nutrient-export like Leonard also mentioned, namely macro-algae.  I had detectable amounts of nitrate until I employed this method.  If you don't use a more permanent method you may end up relying on the water changes to keep your nitrate levels down.

[JROC]

Leonard,

 

I have to try and clarify this with you a little bit. Okay, first of all, you are not taking into consideration the continued build up of NO3 are you? So the %s would actually not go downthat fast. However, I am not sure I can clearly see in my mind where 50% at one time is any better, if I take out 50% and then wait 7 days to do the next change, and say I have a @5 production per day (high side hopefully!) then in 7 days I am back to 64%, then 32%, then 46%....etc. So either way, it is going to take a while. Furthermore, is it not possible that to let NO3 and other organics build up for 7-14 days, and then be reduced 50% is much more stressful than to keep them some what stable with small changes every few days? If the frequent small changes outpace the production level of DOC production, then things should tick along nicely. Am I crazy!?

[camustang]

There is a technique called "Multiple-Step Water Change".  It involves doing a water change, say 80% (leaving 20%) and then filling the tank back up to 40%, then back down to 20% again.  Go up to 40% one last time, and then back down to 20%.  Finally go back up to 100%.  In this example, your tank would go from 100ppm to 5ppm in one set of water changes.

 

This takes into account the same principles listed above as far as the greatly diminished effectiveness of very small water changes over a week or more.  Of course, this method is only needed when the levels are DRASTICALLY high and need to be reduced quickly.  Otherwise, the more conventional partial changes work fine.  

 

I wish I could say I thought of this, but I didn't.  You can read the article (and see a little animation) here: http://saltaquarium.about.com/library/week...s=water+changes

 

The author also addresses the "sudden" change in water quality, saying:

 

"Some people have expressed concern that the rapid reduction of nitrates would "shock" the tank critters. This is an understandable concern, but under the circumstances wouldn't you think that the rapid reduction of potentially harmful toxins in a tank to be of the utmost importance, and a lot less harmless? It would be like standing in a closed garage with a car engine running, filling the garage with carbon monoxide, and someone telling you not to open the garage door; that the rapid reduction in carbon monoxide levels would in some way be more harmful to you than only reducing their levels by 20%. If it was me in that situation, I would kick the door open as far as it would go."

 

Good article, good idea, and another tool in our arsenal to combat the "bad stuff".

 

Hope this is helpful....

 

-Andrew

[Strife]

i suggest that you keep doing partial water changes daily or every other day till nitrates goes back down...

i dont believe that doing a large volume of water change will help..it would rather cause stress to inhabitants..

 

there are many reasons for nitrate level to go up...

first we have to figure out why/how it happened

because water change might not help you at all...it will just come back up later on

 

overfeeding, not enough water change, filter not being cleaned often, old additives, brand of salt...are some reasons why ammonia, nitrates, and nitrites to go up..

[Leonard]

From experience, I will confidently state that large water changes will not have a negative impact on fauna or flora provided you make sure the physical parameters of the waters match up (temperature and salinity).  The quote andrew provided from the article is a good one, although I don't see much merit in "Multiple Step" water changes except when you absolutely need to drop the concentration by 95%.  I'd find a single 90% water change so much easier to do.

 

I understand that nutrients are going to acculmulate again once you do any water change, but this build up is linear and constant, so it's a non-issue.  Bottom line is if you do 10% water changes, you'll need to do SEVEN water changes to reduce the concentration by 50% versus ONE single 50% water change.  If you're a glutton for work, go ahead and do 7 water changes to slowly dilute the water.  But I'm telling you that your inhabitants won't mind a single large water change, and might possibly prefer it over being subjected to living in subpar conditions for the extra few weeks.

[Leonard]

FWIW, I completely agree with Stryf3 on one issue: You need to find the source of nutrients and stem it off there.  Most likely candidates for import include food and make-up water.  If you're not using purified water or if you're excessively feeding, you need to change these practices.

 

Of course, since the tank is new, all these nutrients is probably from the original die-off on the live rock.  A water change will effectively reduce this level.  If nutrients continue to build at alarming rates, find out where they're coming from, and figure out ways to export them.  Nutrient balancing, after all, is achieving the ideal of equal import to equal export.

 

(Edited by Leonard at 12:36 pm on June 19, 2002)