Testing Part Two - Nitrogen Nitpicks
Welcome back to our series on testing for the home marine aquarium. Last week we delved into the basics, water temperature and salinity. This week we need to talk about some more advanced testing. There is a huge variety of test kits and probes available to the hobbyist. Which ones are relevant? Well, the short answer is all of them have their uses, but the most important ones for you as a first time aquarium keeper are all of the nitrogen tests including Ammonia (NH3), Nitrite(NO2-) and Nitrate (NO3-).
Nitrogen tests are important because they are the byproduct of biological processes, (so you WILL have them in your aquarium in one form or another) and are toxic to varying degrees based on the form of the molecule we're talking about. Luckily, nitrogen compounds go through a natural breakdown process given enough time and the right conditions and thus are fairly easily “filtered.” We're going to wildly oversimplify this to make it relevant and easier to understand; Ammonia can be turned into nitrite, and nitrite to nitrate by common bacteria, which will colonize your filter system and aquarium environment. Truthfully, there is little you can do to stop this, and luckily you don't want to stop it. Of the three, nitrate is the least toxic and the hardest to deal with as it can only be removed by bacteria that like conditions without oxygen, uptake by plants / algae, or by gassing off. This is one of the main reasons some aquarists like to utilize “refugium” filters, but that is another article.
Ammonia is the “rawest” form and the most toxic to the critters in your care. It will be the first of the three nitrogenous compounds to show up after you've set up an aquarium, and you'll need to test for it until it is gone and again after adding any new fish as the increase in feeding could theoretically cause Ammonia to rear its head again. Overlapping this timeframe, you should also be testing for Nitrite, which is also very bad for the fish and inverts common to aquariums. Over the first couple weeks these two tests should start to taper off and in the end should read zero. As they drop off, you will generally notice a rise in nitrate, and this will taper off as well, though it may never get down to zero, you want to maintain it at as low a concentration as possible; generally less than .5ppm, though levels as high as 5ppm and as low as .1ppm can be maintained successfully depending on how the aquarium is stocked. Excess nitrate will fuel wild algal blooms causing a myriad of issues. There are many supplements are on the market these days for seeding aquariums with bacteria to jump start this bio-filter. We stock, sell and use Dr. Tim's in house. If you want to utilize this technology, Dr. Tim's has our seal of approval.
Other kits you will frequently see available are for testing pH, calcium and alkalinity. This being said, if you are using a quality salt and reverse osmosis filtered water, you really won't need to delve into any of these tests unless you start keeping very demanding species like Tridacna clams or certain corals. Quality salts like Tropic Marin are made to such a high degree of precision that they contain everything your fish and inverts will need. By doing regular water changes, they can maintain an excellent level of alkalinity and calcium at a very stable pH without ever having to supplement.
If you live in an area where you have excellent well water and can use tap water for your aquarium then regularly testing your pH can become more important as your water will likely have a profile that is different from the RO water expected by the salt maker and could also go through seasonal variation. pH is difficult to describe accurately, the easy way to understand it is how acidic or basic is the water, and for our purposes this will suffice. (It's actually a measure of the negative logarithm of the effective hydrogen-ion concentration in gram equivalents per liter). 0 is the acidic limit, while 14 is the basic limit , thus 7 is neutral. Today's ocean averages about 8.1 and most aquariums salts, properly mixed, will result in a pH between 8.0 and 8.4. If your results are outside of that range, you should try new probe or test kit. If after retesting your results are still outside of this range, then you will need to look into buffering or acidifying (even with tap water, this is very unlikely). When your aquarium starts becoming more heavily stocked, daily pH checks can be a valuable indicator for other problems in densely populated aquariums.
Your LFS will likely stock and sell a couple/few different brands of test kit. Ask them which ones they like the best, and many shops will give you a demo on how to use them. There are many quality tests on the market these days.
Every new aquarium should be tested for all three nitrogen compounds daily until ammonia and nitrite disappear and nitrate drops to under 1ppm. Fish and inverts should never be added before this. After this, Ammonia and nitrite readings can slow down to weekly, but you should keep testing nitrate every day until you start getting very stable and acceptable readings. After a couple weeks of numbers under 1 you can slow this testing down to a couple times a week. Anytime new fish are added you should start testing all 3 nitrogen compounds every day again, and a full battery of tests is always good to do right after a water change.
All testing should be done at the same time of day, as day and night cycles can shift pH, and the time away from the last feeding can shift a nitrate reading as well. These are enough test for the basic hobbyist to have success with a reasonably stocked aquarium and very regular water changes. If your aquarium develops into a wonderland of clams and SPS corals, more intense and regular testing will be necessary, but alas, that is another article. Keep excellent records of your testing results, water sources, as well as your stocking and feeding history. A huge amount of experience can be gained by looking back over time and seeing how switches in process affected your aquarium. Now go forth, and start testing!