Reef Tank Water Parameters

Water Chemistry...I'm In My Element

As we are slowly acquiring new coral within our 12 gallon (45 L) nano aquarium, it is becoming essential to monitor the water parameters within our system. These values are imperative towards coral health & can be an indicator when issues arise within the aquarium. Especially within a nano system in which dramatic fluctuations can happen suddenly. Water chemistry within reef tanks can quickly become confusing and leave you feeling like a toddler sinking in the deep end of the pool. Well allow us to toss you some water wings as we help wade through the water parameters we currently measure within our system and examine why these elements are important within a reef aquarium. ​

​Temperature: 74 - 84 F (23 - 28 C)
Temperature is one of those variables where the exact number (as long as it is within acceptable parameters) is not as important as consistency. We currently keep our nano aquarium at 78 F (26 C). However during the summer months, we anticipate the temperature possibly rising a couple degrees as we live in a warmer region and maintain our ambient house temperature between 78 - 80 F (26 -27 C) .
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Consider purchasing a type of heater controller to monitor temperatures within your aquarium

Salinity: Specific Gravity of 1.023 - 1.027
Salinity is measuring the amount of salt dissolved within the water column. The easiest method to measure this parameter is through measuring the specific gravity of your aquarium water. We maintain our aquarium at 1.026 and conduct daily top offs of RO/DI water to account for evaporation. Keep in mind that as water evaporates from your aquarium, the salt is left behind causing salinity levels to increase. An auto-top off (ATO) system can adjust for these fluctuations as well.

Specific Gravity Reading through the Refractometer

Salinity Refractometer for Measuring Specific Gravity

Phosphate: <.03 ppm
Phosphate levels should be kept at levels lower than .03 ppm within a reef aquarium. Levels reaching .3 ppm are considered to be problematic. Higher levels are detrimental in two ways. First, higher levels of phosphate can inhibit the calcification of corals. This means that they hinder the development of corals calcium carbonate skeleton, thus stunting their growth. Second, phosphate serves as a key ingredient in the growth of algae. Keeping lower phosphate levels will aid in deterring algae growth. To maintain lower phosphate levels in our aquarium, we rely upon Bulk Reef Supply’s Bulk GFO Granular Ferric Oxide (High Capacity). Additionally, chateo algae grown within the refugium section of a sump can aid in phosphate uptake from the water column.
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We keep our GFO within a mesh bag for our system; however, it will provide greater efficiency if it is housed within a media reactor in a sump

Nitrate: 0 ppm
Nitrate is the end product of the nitrogen cycle and signifies a cycled tank. The ideal reef tank should have negligible levels of nitrate. However if measurable levels of nitrate are present within the tank, it does not mean the imminent death of your fish and coral. Elevated nitrate levels though hinder coral coloration and inhibit skeletal growth. Additionally, elevated nitrates spur algae growth. We recommend keeping nitrate levels as close to zero as possible and refrain from having levels rise above 10 ppm. If you experience higher nitrate levels, investigate your feeding schedule as excess nitrogen from food will inevitably lead to nitrates. Also consider relying on the addition of protein skimmers or chateo algae to your system to assist in keeping levels down.
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Ammonia: 0 ppm
Ammonia is excreted by fish and invertebrates through waste. High concentrations of ammonia can lead to burning of sensitive animal tissues. Ammonia levels should remain untraceable by standard testing kits in stable aquariums (tanks typically over 2 months old). Should you find detectable levels of ammonia, this indicates a breakdown within your nitrogen cycle which requires an evaluation of tank parameters in order to determine its cause.
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Nitrite: 0 ppm
Nitrite is the intermediary step between ammonia and nitrate within the nitrogen cycle. Just as in ammonia, nitrite levels should be undetectable by standard aquarium kits. While nitrite levels are not an immediate problem to corals, once again, it does indicate a breakdown within the nitrogen cycle of the aquarium and is not typically witnessed in stable, established aquariums.

API Water Testing Kits for Ammonia, Nitrite & Nitrate

pH: 8.2 - 8.4
pH values measure the amount of molar concentration of hydrogen ions within a solution thus determining a solutions basicity or acidity. Highly acidic solutions have a reading of 0 while highly basic solutions have a reading of 14, with neutral solutions having a pH reading 7. In many aquarium systems, there are fluctuations of pH readings throughout the day. Higher values are typically witnessed when brighter lighting drives photosynthesis while lower values are found during the night. Our nano aquarium runs within a pH range of 7.8 - 8.3 depending on the time of day. While slight fluctuations are considered normal, larger pH changes can be harmful to both fish and corals. 

High Range pH Testing Kit from API

Alkalinity: 7 - 11 dKH or 2.5 - 4 meq/L (125 - 200 ppm CaCO3 equivalents)
Defining and explaining alkalinity could comprise an article all on its own (not to mention providing a powerful sedative & headache inducing agent). I will avoid the sleep aid and migraine route by trying to simplify alkalinity to its two most important aspects in relation to reef tanks.
1.) Alkalinity determines the buffering capacity of the water column. In other words, alkalinity reflects the water’s ability to resist pH swings. Higher alkalinity values provide water with a greater resistance towards pH changes. Remember that stability is key within reef aquariums and avoiding dramatic pH changes is imperative.  
2.) Alkalinity also influences the calcification rates of coral. In order to maintain healthy, growing coral it is important to keep alkalinity within the suggested ranges. Alkalinity provides a measurement of bicarbonate in water which corals utiizle for their calcium carbonate skeletons.
Buffers can be utilized in order to maintain proper alkalinity levels, however, corrections should not attempt to be made in one dosing as this could cause pH swings.

Salifert KH / Alkalinity Testing Kit

Calcium: 380 - 450 ppm
Calcium is an essential element which corals utilize for expanding their skeletons (calcification). Growing corals can quickly exhaust an aquarium of free floating calcium suspended within the water column. Should levels drop below 360 ppm, coral have a difficult time extracting the calcium they need for growth and could become stunted if left in these conditions for long. For this reason, calcium additive methods become an essential component to healthy reef aquaria.

API Testing Kit for Calcium

Magnesium: 1250 - 1350 ppm
Magnesium’s importance to a reef aquarium is linked with calcium and alkalinity balance. Explaining the precise chemsitry behind this relationship is enough to make anyone’s head spin. Sufice to say, that magnesium’s presence within the water column allows for greater addition of calcium without lowering the alkalinity of your aquarium (don’t forget this could lead to pH swings). If you find it challenging to maintain necessary calcium or alkalinity levels within your system, lack of magnesium could be your problem.

Salifert Magnesium Testing Kit

The above parameters we regularly monitor within our nano aquarium. While these are the key elements which should be monitored frequently, there are other trace elements that provide crucial benefits to coral as well. Silica, Iron, Strontium, Iodine, and Boron are all found within seawater and provide their own unique attributes towards overall coral health. Their parameters and exact contribution towards coral will be reviewed in a future article.

Hopefully we have been able to provide some clarity to the basics of water chemistry. Several chemical tests exist on the market to assist you in determining the parameters found within your aquarium. And here you thought you would never have to titrate again past high school chemistry!

That's it for this time! Keep Krill'in!