There are plenty of times I talk with fellow reefers or hobbyists about high levels of nitrates or phosphates in the display tank and you can just see the frustration weighing down on them like a 1,000-pound gorilla. Most of the time the list of steps taken include less feeding, more water changes, changing salt mixtures, changing foods, or adding carbon or granular ferric oxide like Phosban . I usually ask “have you checked your water source?” The response is typically “no.” If we are noticing high levels in our tank, we need to figure out exactly where they are coming from and my suggestion is to start at the source — the tap.

City and well water can contain high levels of both nitrate and phosphate and many hobbyists make the efforts to eliminate this through either buying filter water or a reverse osmosis (RO) filtration unit for their home. To really understand what you are getting and what you are putting in your tank, I recommend testing the entire chain of water, from tap to post-filter to pre-salt to post-salt, to see exactly where you stand.

Invest in a quality reverse osmosis filter.

The best preventative measure is spending the money and get a quality RO unit with the highest production rating as possible. You can find these for anywhere from $100 and up. Your unit should be at least a 3-stage unit consisting of a sediment, carbon and RO filter and the more you can get the better. It is also advisable to get a deionization stage since this will produce nearly pure water for your system. If you are buying filtered water, don’t trust the advertising.–you don’t know how good the filters are and how often they are changed. If possible, purchase a hand held TDS (total dissolved solids) meter since this will help determine how effective is your system.

Hand held TDS meter.

Let’s assume you have a home filtration unit and that it is installed correctly. The first thing to do is to let the tap water run for about a minute to make sure you are a getting a good sample of the source water and not just water that has been sitting in your pipes. After letting it run, take a sample of the water for testing.

Now let’s take some base readings. First take your TDS meter and see how much junk is floating in your water. The meter will read in PPM or parts per million and this represents how much particulate (can be minerals, organic compounds, etc.) is in the water. Next get your aquarium test kits out and measure across the board for pH, ammonia, nitrites, nitrates and phosphates. Mark all of these down somewhere and every so often, retest as the water chemistry changes throughout the year.

With these readings, we will now know how much work our filters will have to do. If you have high readings, then you can pretty much know you’ll have to be doing more filter changes and keeping a closer eye on the system. The more junk, the more work and the quicker the filters will become blocked. If they are low, then you’ll probably not have to change the filters so often and get more mileage out of them.

Now start your water filter and let it run for a few minutes to flush out all the water stuck in the system. I typically let mine run for about five minutes before collecting a sample in a clean plastic cup or container. If you are running a DI unit, see if you can get a reading right after the RC filter to see how your RO filter is performing. You guessed it, test this sample across the board as well and compare the results to your base readings. For those of you with a DI unit, run the water through it for a few minutes, sample and test.

The purpose of testing each stage is to see exactly where we are after each step and getting to know the basic water chemistry running in our house both pre- and post-filter. Hopefully any readings of ammonia, nitrite, nitrate and phosphate after the filter are now at zero. If you have any amount showing up, we know we have a problem somewhere along the line from the tap, through the filter. Now is a good time to check and replace any old or exhausted filters, flush or reseat the RO membrane or change our supply of DI resin.

If your readings are good after the filtration, let’s see what happens when we add our salt mixture. NOTE: Always add your salt mix to your water rather than water to your salt mix. Water can only hold so much salt and this can have adverse affects on your mixture. So please make up as much water as you need for your water change FIRST, and then add the salt to that.
After your water reservoir, bucket or tub is filled with water and the proper amount of salt is added and mixed (and your final specific gravity is acquired), test your water again. This will help eliminate the possibilities of any amounts of phosphate or nitrate in the salt mix. Hopefully you are reading zero on both.

By following these simple steps, you can know exactly what you are dealing with and potentially adding to your system. Many people use the water filtration vending machines and trust they are getting quality, filtered water. If you are going this route, do yourself and your tank’s inhabitants a favor and test each time! Better yet, invest in an RO/DI unit for the home–you’ll save money in the long run.