The end product of biological activity, and the end product of organic breakdown is a compound known to hobbyists as nitrates. In aquariums it occurs bound with many other compounds or chemicals, and not on its own.

Untold articles and sections of books have been written on how nitrates appear in aquariums. Most of these articles make it clear that high levels of nitrate are detrimental and can cause many types of disease outbreaks. All these articles usually point out that nitrates are toxic if their levels become too high. Many of these articles are referenced by recent authors to illustrate what levels of nitrate they consider safe.

What is often overlooked, is that a lot of these articles were written several years ago, when reef tanks where not even on the horizon. This makes their use as a reference to justify certain nitrate levels as being acceptable, doubtful to say the least., when applied to the reef tank.

Why such does not occur to authors writing about reef aquariums is not clear. Perhaps they assume that invertebrates and fish act alike in their responses to levels of nitrate (and also phosphate) pollution. Such is, in my experience, a great mistake. They do not!

Corals and invertebrates come from environments where the total nitrate levels are extremely low, close to zero ppm in many cases, and not much more than 4 ppm of nitrate at the high end. Suggesting that corals and invertebrate will do well in aquariums with nitrate levels of 15 ppm is, therefore, in my opinion, totally misleading. And that is indeed the number you will often find as a suggestion, even in very recently written articles.

• NO3, or below 1 ppm of nitrogen nitrate, N-NO3. Check your test to determine which of these two measurements applies to your situation. Most of the ones on the market measure N-NO3 and the 1 ppm limit is, therefore the one that applies.

Nitrate removal from the aquarium is a complex matter. It occurs in many forms, but perhaps the most frequently suggested, and rightfully so, is water changes. While such may not bring the nitrate levels down to zero ppm, or perhaps not even to lower than 5 ppm, it is certainly a step in the right direction. Water changes must, as we have already seen, be performed for other reasons anyway. You must make sure, however, that the water used to do so, and the salt used to prepare that water, do not contain nitrates themselves. Such would be totally counterproductive.

At times you may hear that nitrate (and phosphate) are a necessary nutrient of many life forms in the aquarium (even advertisers make such claims). Such is, of course, correct. What such statements usually fail to mention, however, is that nitrate (and phosphate) is already present in large enough quantities in aquarium water, making it totally unnecessary to add more as part of the water or the salt used.

If corals and invertebrates need to be kept at nitrate levels as low as 1 ppm of N-NO3, adding nitrate as part of the water or salt used, is really bad advice. Don't do it. Removing nitrate (and phosphate) is difficult enough as it is, that you do not need to complicate it even more by increasing its levels knowingly. Check the water you use, and also the salt, for nitrates. If either contains any, change your supply source. Take my advice, do it.

Another method used to lower nitrates is the use of compounds that absorb it. X-nitrate, Thiel*Aqua*Tech's answer to the nitrate problem, is one such compound, and one that works extremely well. Because of its price, however, it is recommended that you first bring down the nitrate levels by water changes to the range of 15 ppm NO3, and then start using X-nitrate. Such is also that company's recommendation. A 50 gallon treatment lot cost around $22.00 at the time of this writing, and lasts a couple of months.

All you need to do is place X-nitrate in line with the water circulation. The more water flows through it, the better it will work for you. Placing it in a bag is not the most efficient way to use the compound. Indeed, water has a tendency to flow by and over the bag, and not through it. If the water does not flow through the bag, it also does not flow through the compound. Place some of it in your corner overflow box, or place it in the surface skimming siphon. Use a tray right underneath your biological chamber, or fill a canister filter with it, and run the canister filter by taking water from the sump of the filter and discharging the water either in the tank, or back into the sump. Layer the X-nitrate between floss to prevent it from getting into the tank, or into the pump and motor of the canister filter.

X-nitrate is a granular compound that will come to you some-what moist, rinse it well to remove dust and pulverized compound, and you are ready to place it in service. I use X-nitrate myself on a 135 gallon reef at my home which consistently shows very low levels of nitrate: below 1 ppm of N-NO3.

Lastly, hobbyists also use devices called denitrators. These outside filters, through which water is flowed slowly and to which a special nutrient must be added to promote nitrate respiration by the bacteria present in the filter, are extremely efficient, but a little more touchy. They need regular attention, especially in the beginning.

To make the water from the tank, the water that contains the nitrate that you want to eliminate, flow slowly through the denitrator, you must drip water slowly into the denitrator, rather than flowing water through the unit. That is where the problem is.

To establish a drip you must use airline style tubing and start a siphon effect, while at the same time compressing the airline tubing until the desired drip rate is attained. This leaves a very small opening inside the tubing for water to pass through, and that opening can easily clog. Such makes the drip slower at first, and then it may stop altogether. When this happens the filter goes anaerobic in matter of hours. Hydrogen sulfide is then produced. Since the filter is at a standstill, the noxious hydrogen sulfide is not being added to the tank, and the damage that occurred is limited to the hobbyist having to restart the denitrator anew after cleaning it out completely. Not a pleasant task, but at least nothing detrimental to the tank's life forms has happened. It will take 4 to 5 weeks before the denitrator is functional again.

Even when the filter runs but runs too slowly, hydrogen sulfide may be produced, but this time it is evacuated slowly from the denitrator and pushed into the tank's water. Such is of course very dangerous as we have already seen. Again the unit must be taken out of line, cleaned and restarted. Unpleasant to do, but not as cumbersome as restarting completely from scratch. After water has been added, and the filter is restarted, it may take up to a week for the unit to operate properly again.

Several companies offer both the units and the nutrients, but some offer only the unit and claim that no nutrient is necessary. Such is completely erroneous.

The chemical process, when methanol is used as a carbon source (the nutrient), can be summarized as follows:

NO3 + 5/6 CH3OH ----> ½ N2 + 5/6 CO2 + 7/6 H2O + OH

Because methanol is potentially dangerous when excess amounts are used, other carbon sources are often added in its place. These include ethanol, glucose, acetate and so on. Which nutrient you use is not as critical as using one. If you don't, the so-called denitrification process can not take place completely, and the filter will be very hard to regulate.

The reasoning and explanations outlined in 5.18 when talking about nitrates apply to phosphates as well. Phosphates, in large amounts, are detrimental to corals and invertebrates. In addition, large amounts of phosphate invariably give rise to the appearance of hard to eradicate micro-algae that make the tank look unsightly in a very short period of time, as many of you may have found out.

The recommended maximum level of PO4 is 0.1 ppm, while less would be much better. My own 135 gallon aquarium tests less than 0.05 ppm of orthophosphate.

Keep phosphates in your own aquarium as low as you can. Use caution with the water you add, and with the salt you use. Several brands tested contain phosphate in larger quantities than you should feel comfortable with. Be careful too with activated carbon. Many brands sold in the hobby leach phosphates into your tank.

To ensure that your water, salt and activated carbon do not, all you need to do is test them for phosphate levels. First test the water you use. Make sure it does not contain phosphates. Then add salt, respectively activated carbon, to some of that water, wait a couple of hours and test again. If your test shows phosphate levels higher than what you originally had, you know that the phosphate is coming from the salt or the activated carbon.

In the latter case my recommendation is that you use a different type of salt, and a different activated carbon, if such is necessary. If you do not own a phosphate test yet, you should get one soon. Both qualitative and quantitative tests are now available. The former is less expensive and can be obtained from TAT and its dealers. PAT, who already sell an oxygen test, now also offer an orthophosphate one.

Although your tank will also contain organic phosphates, no tests presently exist that the hobbyist has access to. Organic phosphate is mineralized by bacterial activity, and will show up in your testing as orthophosphate once that process has been completed. Testing for orthophosphate is all you need to do.

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