Today we are going to share which water parameters you need to test for in a fish-only or reef aquarium, explain how these parameters effect fish and coral as well as provide tips on how to choose the right test kits for your tank.

Some hobbyists claim they can tell how good or bad their water quality is just by looking at the tank. The reality is when the water quality is so poor that you can tell just by looking at it, you've already subjected your fish and coral to lousy living conditions far longer than you should have and fixing the problem will now require greater effort.

Keeping your aquarium water parameters stable and at ideal levels is crucial to the health and well-being of the animals in your care. That’s why it’s essential to test your water regularly and log the results. Actively monitoring your water quality helps you identify trends or notice changes before they become problematic, making it easier to resolve any issues that may be develop.

Tests to Perform for Fish-Only Aquariums

For a fish-only system, you should test pH, Alkalinity, Ammonia, Nitrite and Nitrate.

pH is the measure of acidity or basicity. Fish and coral can fall ill or even perish if your aquarium pH falls outside acceptable ranges. Tank pH can be affected by a range of factors and should therefore be monitored at all times. Stability is the keyword with pH because large swings in pH level can really stress out your aquarium inhabitants.

Alkalinity is somewhat complex, but is perhaps best understood by thinking of it as the measure of bicarbonate in your aquarium water. A properly maintained alkalinity level makes it much easier to keep pH stable and will provide the necessary components for corals to grow and build a skeleton. Testing should be performed weekly in most cases.

Ammonia and Nitrite are two of the basic waste parameters and are products of the metabolic processes of the nitrogen cycle. They are both extremely toxic to fish and corals and should never be present in your aquarium outside of the cycling process. If either is present in your aquarium, it is the result of insufficient biological filtration and/or an overstocked aquarium. Testing these parameters is usually only necessary while cycling your aquarium, but it's not a bad idea to check them monthly or when you suspect something may be wrong with your tank.

Nitrate is one of the final products of the nitrogen cycle and should be tested weekly. This will help you to establish a regular filter maintenance and water change schedule. When nitrate begins to rise, you know it is time to clean your filtration equipment and perform a water change.

API's Saltwater Master Test Kit is one of the most popular and affordable options for testing a fish-only system. They are easy to use and the results are precise enough to help most fish-only aquarium keepers avoid major problems.

Tests to Perform for Reef Aquariums

When caring for a reef aquarium, in addition to the aforementioned parameters, you’ll also want to test the calcium, magnesium and phosphate levels in your tank.

Calcium is used by corals along with bicarbonates and other elements to grow and build their skeleton. When you are adding corals to your tank, you should test your calcium levels daily. Once you identify how much calcium you’ll need to supplement to keep your corals growing, you may begin to do so and reduce testing frequency to once per week.

Magnesium is important because it influences calcium and alkalinity levels and is also used by corals to grow and build their skeleton. Testing should be done weekly to monitor demand.   Supplementation is often required, especially in aquariums that are heavily stocked with stony corals.

Phosphate is another important parameter to test for because it fuels algae growth and inhibits your corals’ ability to utilize calcium. The phosphate level in a reef aquarium should be kept below 0.05 ppm. Higher levels can lead to algae issues and cause corals to brown out or deteriorate. Conversely, having an absolute zero phosphate level can starve corals. You can keep your phosphate level low by using one of the many phosphate-reducing filter media options available or through supplementation. You can help prevent phosphate from entering your aquarium by using RO/DI filtered water that measures 0 total dissolved solids (TDS). Testing for phosphate in a fish-only aquarium can also be helpful to keep nuisance algae at bay.

Getting accurate test results is important when caring for a reef aquarium. Red Sea, Salifert and ELOS are widely considered the most accurate and easy to use liquid test kits by reefkeepers. Hanna Checker Colorimeters are another option and a great alternative for hobbyists that find color recognition-type test kits difficult to interpret. The electronic monitors offered by American Marine are even more helpful because they give you a constant electronic reading, although they must be checked regularly to maintain their accuracy.

Now that you have a general understanding of the key parameters to test for, you can perform them regularly so you’ll know how much to supplement, how often and when to change your water.

Tests to Improve Coral Color and Growth

But the fun doesn't stop there!

Natural seawater contains a variety of dissolved and suspended material that fish and corals need to thrive. Advanced reefkeepers find that testing and maintaining ideal levels of iodine, strontium, potassium, boron and iron helps them not only grow but improve the coloration of their corals.

These materials are all considered minor or trace elements and each plays a role in the survival and growth of our reef inhabitants.  Iodine helps soft corals and invertebrates grow. Strontium is important for stony corals and clams to build skeletons. Potassium helps with blue coloration in corals and boron helps with red. Iron is crucial to the growth of macro algae and is great to test for if you are keeping a refugium.

Salifert and Red Sea offer the best test kits for minor elements.  If you are testing for these levels, a weekly regimen is probably best. A log of your test results is also helpful. For most hobbyists, these levels can be maintained by simply performing regular water changes. In heavily stocked and mature reefs, supplementation may be required and is possible using a comprehensive trace element additive or a parameter-specific additive offered by brands like Red Sea or Brightwell Aquatics.

Having a list handy of ideal reef tank parameters is always helpful. That way when you test your water, you'll be able to easily tell if your parameters are out of whack.

We could talk for hours about water chemistry, but hopefully we've packed enough information into this video to help you grasp the basics. If you'd like to learn more, please leave us a comment with your questions or contact our aquarium experts for free advice by phone or email. We certainly appreciate you tuning in! Don't forget to subscribe to our YouTube channel for more helpful tips and until next time… take care and happy reefkeeping.

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