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Tools For Managing Nitrate

in Freshwater Aquariums


 Part I: INTRODUCTION
	What is nitrate?
	How can I tell if nitrate is too high?
	Why is high nitrate bad?
	What is the recommended level for nitrate in freshwater tanks?

 Part II: BASIC MAINTENANCE TO CURB NITRATE PRODUCTION
	What is considered "basic maintenance"?
	Getting a dirty tank back in shape!

 Part III: TOOLS BEYOND BASIC MAINTENANCE
	Beyond Basic Maintenance
		Plants
		Chemical Filtration
			Ammonia chips to reduce nitrate production
			Resins to absorb nitrate directly 
		Denitrator media
			Low-flow media for growing anerobic bacteria
			High-flow media for growing anerobic bacteria
		Denitrators
			Commercial Denitrators
			Coil Denitrators (DIY)		
	Summary

 Part IV: HOW TO DETERMINE WHICH TOOLS ARE BEST FOR YOUR SITUATION

 Part V: A REAL TIME EXPERIMENT IN NITRATE MANAGEMENT









PART I: INTRODUCTION


What Is Nitrate?
The final product of a healthy biological filter is nitrate.

Ammonia and nitr-i-te are continually created in the tank by fish waste, uneaten food and decaying plants, and eventually get converted to nitrate; so nitrate is being produced all the time. Since aquariums are closed systems, nitrate levels can rise out of hand unless kept in check.

Although most freshwater fish can be pretty tolerant of nitrate [when it builds slowly] high levels of nitrate are considered indicative of poor water quality. A high nitrate count (over 20ppm) is normally attributed to inadequate water changes, unvacuumed substrate, dirty filters, or a combination of those.

In a tank where the maintenance routine has not kept pace with nitrate production, it is not unusual to find nitrate in excess of 300ppm. Unclean filters and substrate make more ammonia available to the biofilter. More ammonia = more nitrate production. Therefore regular maintenance goes a long way to curbing rising nitrate levels.

That said, under certain conditions - especially in fish only tanks - even vigilant maintenance doesn't cancel out nitrate production. In these cases alternative solutions must supplement regular maintenance to keep nitrate levels under control.

How can I tell if nitrate is too high?
Not by looking. :) Water that is excessive in nitrate can appear very clear and look healthy. Nitrate does not color the water, nor does it have an odor. To learn your nitrate level you must use a test kit. These are available at local fish stores. NOTE: Make sure to get a nitrAte test kit, and not a nitrite test kit.

Test kits are made by several different companies and like all aquarium test kits, are read according to color changes in the sample vial. (The sample vial is filled with your tank water and some additives from the kit, then the color of the water changes depending on the amount of nitrate present. You simply match the color to a color chart which has a corresponding ppm count.) Some kits, like Tetra's Nitrate Test kit, measure in larger increments. That is, from 0ppm (bright yellow), the first distinct color change indicates a jump to 12.5ppm (gold). If the color falls somewhere between, so is your nitrate count. Therefore if you want to maintain nitrate at a precise level less than 12ppm you should get a test kit that has distinct color changes between 0ppm and 12ppm. (Some have color changes between 0ppm, 2.5ppm, 5ppm, etc. This eliminates guess work.) The Tetra kit is good for those who are less anal and figure "anything between 0 and 12.5ppm is okay".

Why is high nitrate bad?
Even though most freshwater fish can tolerate very high levels of nitrate when they build slowly, there is little doubt that keeping fish in water that is lower in nitrate is healthier. Lower nitrate indicates cleaner, more pollutant-free water.

Perhaps the biggest reason to avoid high nitrate levels is algae. Algae will colonize wherever water is rich in nutrients and light. Since nitrate is a natural fertilizer, high levels invite algae. A little algae is fine, but too much of it is a bane. It consumes oxygen, can smother plants, and once out of hand, is unsightly and tough to get rid of. (Ridding yourself of algae in a ten or twenty gallon tank is bad enough, but try cleaning a tank that's eight feet long by two feet high ... up on a three foot stand!) It's far easier to avoid algae in the first place by keeping nitrate levels low. For those with large fish-only tanks "low nitrate" has become a mantra.

What's the recommended level for nitrate?
Generally speaking ~5ppm per liter is considered ideal. Some sources claim that maintaining zero nitrate can lead to cyanobacteria, therefore 5ppm seems to be the level of choice but anything between 5ppm and 10ppm is fine. The lower you keep nitrate levels, the more "bumper" you have if you occasionally miss your normal maintenance routine due to vacation or what have you. Levels at 20ppm and greater are generally considered high, with anything over 50ppm being very high.
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PART II: BASIC MAINTENANCE TO CURB NITRATE PRODUCTION

What's considered basic maintenance?
No matter what your particular situation is there are things you should do to maintain a healthy aquarium and reduce nitrate production. Whatever other steps you might take, they should be supplemental to the following basic regime:



If you have been following the above guidelines yet your nitrate is higher than 20ppm, test your tap water. If your tap water contains nitrate you might have to invest in a water purifyer.

Barring nitrate in your tap, if you are already following the above guidelines but your nitrate is high, try increasing your water changes to 25% each week. If that still isn't enough to keep nitrate levels in check, you could consider reducing your fishload. Most local fish stores are happy to take healthy fish off your hands whether you purchased them there or not, as long as you're not looking for credit (though you could try). The fish store will have to quarantine, watch, and may proactively treat any fish you give them before selling it, so they will earn any small profit they make. Bottom line is they would be doing you a favor and you'd be doing the fish a favor by giving it a chance at a second home.

Assuming your fishload will remain unchanged, however, you may need to employ additional measures as discussed in Beyond The Basics.

NOTE: If nitrates are in excess of 50ppm, make an effort to bring them down gradually. Taking nitrate from excessive levels to zero all at once could shock your fish. For more on this read on, otherwise you can Swim Back To Main Index.


Getting a dirty tank back in shape!
Okay, so you've tested for nitrates and they're so high they're off scale. You admit you haven't been maintaining your tank like you should, but heck, it looked clean enough! ("Except for that ongoing algae problem!" ;-) And now you know why! And you're ready to deal with it...

Cleaning a tank completely from top to bottom should not be done in one day because going from high nitrates and generally polluted water to absolutely clear water could be a physical shock to your fish, as it would likely radically change the water chemistry. The change should be made over a period of days. Also, large water changes, thorough vacuuming and filter-cleanings should not take place on the same day as this could adversely affect your biofilter.

So here's one safe way to clean up the tank: lightly vacuum your substrate until you've drained off no more than 15% of your tank water into a bucket. Wait for the dirt to settle, then rinse your filters clean in this water. If the water is too dirty to rinse debris from your filters, dump it. Instead fill the bucket with some tap of the same temperature as the tank water and condition the bucket water, (chlorine and chloramine is bad for the biofilter), then gently rinse the filters clean in this water and replace the filters in the tank. Dump the bucket water. Make up new conditioned water to put in your tank. (You only did a small water change because you cleaned your filters. If you have a BioWheel filter and did not have to rinse the wheel itself, you can do a larger water change of 25% and a more thorough vacuuming.)

While your filters are recovering over the next few days you can reduce further pollution by cutting back on feeding that week, and by trimming and removing any dead or decaying vegetation.

Continue to vacuum lightly once a day, going a little deeper into the gravel each time. Drain off no more than 10% of the water each day. (We dropped from 15% to 10% because your filters are still in recovery. Otherwise do 15%-20% a day.)

Once the substrate is clean the water should also look better, as should the fish! Test the nitrate levels again at this point. If they are not down to the desired level, keep changing 10% of the water each day until the desired level. Continue to clean your filters once a week as well. [Click here if you have a UGF.]

When nitrate levels are down to about 5ppm, follow the basic guidelines of weekly water changes, filter cleanings as needed, avoid over feeding, etc., and monitor nitrate readings weekly for the next month or so until you are sure that your new routine is keeping levels steady. If nitrate slowly rises you will need to step up your routine. For example, if you're only changing out 10% of the water weekly, try 15%. If you're doing 15%, try 25%. If you tried to get away with changing water every two weeks in the past, you might have to switch to weekly changes; or maybe you've let your filters go too long between cleanings in the past.

The idea is to do everything you can to in terms of normal maintenance to keep your nitrate levels in check. In most instances the above guidelines of regular water changes and cleaning will be enough to maintain acceptable levels of nitrate, but in some cases they are not and you must supplement normal maintenance with further nitrate management tools as outlined in Part III.

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