Nitrate reduction

[mitch]

What % of water should i change out to drop the nitrate levels? It has cycled for 3 weeks now and my nitrates are still at 160 ppm +, no ammonia and no nitrites. I don't want to overdue the water change, anyone have an idea how much to change out at any one time, and over how much time? Also will the live rock and sand help keep the nitrate levels at a safe level with normal water changes being done weekly.

Thanks for everyones help.

 

[lickwidspace]

General Rule is 10-15%, so you dont shock the system...

I have read ppl doinf closer to 25% but that shouldnt be needed, if you do regular changes of a smaller %

 

[gurumasta]

to get them down initially, i would probably do 10% water changes pretty much daily until they got down under 10ppm. there is no livestock in the tank right?

 

[mitch]

No nothing is in the tank right now. Just wondering if i did a 25-30% change at first then 10% a day would hurt, since there is nothing in the tank except for the sand and rock?

 

[NateHanson]

You can do a big water change without hurting anything, but you'll also just see the nitrates come down on their own at some point as the cycle completes. It's the last step of the cycle.

Just to cover some frequent problems, are you using RODI water? Do you have sand as a substrate (as opposed to crushed coral)?

 

[wrassefan]

I would do a 25-30% esp if it is right after cycle and you have hardly anything in the tank....should be ok

 

[mitch]

I'm not using ro water yet, i don't have a ro unit yet. I am buying gallon jugs of distilled water till i can get an ro unit. I am using sand as a substrate, i have regular southdown about 40 lbs. on the bottom and 30 lbs. of live sand on top of that. It's about a 4 inch bed.

Thanks for the help

 

[jacqur]

It doesn't sound like anything abnormal to me. The nitogen cycle hasn't stabilized yet, just need to be patient. If you want to speed things up with a water change, there is no danger in doing larger ones. The 10-15% guideline is when you have a mature system and you don't want to shock the sensitive livestock by changing the water too fast. For cycling, i think bigger is better. The reason is clear if you were to plot your impurity concentration on a graph.

Think of it like this ~ 160ppm with a 10% change leaves ~144ppm. Next change ~130ppm. And so on after a 5 changes you would have ~ 95 ppm. You would never effectively remove all the contaminants by doing small changes.

Conversely, But If you did one large 50% change you would have ~80ppm. Larger changes when cycling are more efficient. Since there is no risk to live stock - this is what I recommend.

 

[offshore]

What size tank?
What's in it? (lr, sand ect)
what kind of skimmer and pumps?
A 100% water change is not out of the question and may be your best bet. The bactiera grows on the rock, glass and substrate not the water.

 

[smcnally]

For cycling, i think bigger is better.

I'm not going to disagree with you, because I don't know for sure. But, I read somewhere once that if you do too big of a water change during a cycle, it will prolong it because you don't give the bacteria enough time to populate.

 

[mitch]

90 gallon tank, berlin skimmer, 30 lbs. live sand, 40 lbs. of southdown, 180 lbs. lr, quiet one pump.

 

[shawn]

If ammonia and nitrites are at 0 and nitrates are high, the cycle is over.

I agree with jacqur - if you did a 50% water change, it would get to you 80ppm. Then if you did another 50% water change it would get you to 40ppm. Then if you did another 50% water change it would get you to 20ppm. Get the idea? Now do the math with 10% water changes - 144ppm - 130ppm - 117ppm - 105ppm - etc... - it will take a lot! If you don't have things in the tank that will be sensitive to larger water changes, bigger will get the levels down faster. On the other hand, if there isn't really anything in there, stop feeding and the levels should come down on their own in time. Just don't drop anything sensitive in there while the levels are that high.

 

[MarkO]

A 50% won't necessarilly get you down to 80. Folks have battled nitrates and have said that water changes don't do what they hope.
I recommend you get a RO/DI before doing majoe water changes (it will pay for itself quickly) and maybe add some macro algae (if you don't plan on adding fish for a while).

 

[shawn]

Well, I think the chemistry doesn't lie, so either the people doing the reporting were mistaken about the measured nitrate levels or about the amount of water they changed, or they were dealing with large continuous sources of new nitrate. The assumptions made in the description above were that of an empty (little to no livestock) cycled tank (0 ammonia and 0 nitrites), and therefore no substantial continuos nitrate source. The more livestock or other ammonia source, the less effective the water changes will be in decreasing the nitrate levels due to a continuous replenishing supply.

 

[delta]

sometimes just taking out 50% of the water then dumping 50% volume of new freshly mixed water wont yeild much. but if done in smaller increments over time allowing the smaller amount to mix then remove more then add, mix, remove till 50% is complete is much more effective.

so take 110 -
mix 55 gallons
remove 15 gallon of tank water
add 15 gallons new water
mix 20 for minutes
rinse and repeat

 

[shawn]

sometimes just taking out 50% of the water then dumping 50% volume of new freshly mixed water wont yeild much. but if done in smaller increments over time allowing the smaller amount to mix then remove more then add, mix, remove till 50% is complete is much more effective.

so take 110 -
mix 55 gallons
remove 15 gallon of tank water
add 15 gallons new water
mix 20 for minutes
rinse and repeat

That's a good theory, but science and math doesn't seem to support it. Can you explain why that is better? The reasoning about why it isn't better is that every time subsequent to the first time time you make a water change, you are actually taking out some of the new water you just put in the time before, instead of taking out some more of the old water (image the effect of making one 100% water change vs. two 50% water changes). If interested, I can provide actual numbers for the examples you gave above.

 

[delta]

its not really a mathmatical equation, its like add volume to your tank. in effect it allows you to dilute the nutrients in the tank with out creating a larger system of holding water and does not have any major impact to the biological system of the tank

side note:
if your sump can handle it you can add first, mix then remove

 

[offshore]

After the ammonia and nitrite levels drop to zero, as soon as possible or at least within 5 days, perform a complete water change.


Tip: No water changes should be performed or ammonia destroying products of any kind be added while the tank is cycling, as this only delays and drags out the completion of the process.
Tidy Things Up

Rinse out or replace any type of "mechanical" water filtering materials such as flosses, cartridges, sponges or pads. Clean off the front tank panel, and lightly siphon out any organic waste and/or nuisance type algae that may be on the "surface" of the substrate, and only the surface. Remember, beneficial nitrobacters grow on all surfaces in the aquarium, and at this stage they are still maturing, so you only want to do light maintenance as not to strip them away and weaken their numbers.

 

[RichConley]

from what I've read, like 99% of the bacteria is on surfaces. A good deal of the bacteria in the water is skimmed out too. I dont think water changes will afffect the cycle.

For what its worth, a 50% water change WILL cut your nitrates in half. THe problem is, if theyre still being produced, theyre not gonna stay down for any amount of time.

 

[JohnK]

If the tank has cycled (ammonia to 0, nitrite 0, nitrate accumulating) and there is little to no livestock I would say do a few large water changes with quality RODI make up water. If the water is made up in advance and you move quickly you can change %50 within 10 min. If there is no livestock to speak of then a massive water change won't be a problem.

Nitrate accumulating can be controlled be encouraging denitrification (DSB, losts of LR) and nutrient removal (refugim growing lots of cheato), but it's not part of the initial cycle.