How to Maintain Quality Salt Water for a Saltwater Fish Aquarium

FOWLR AquariumMaintaining quality salt water in your fish only aquarium is vital for successfully keeping marine fishes. Today we're going to look at how to control water quality in a fish only salt water aquarium, meaning there are no corals in the salt water aquarium, just fish and live rock or decorations.

Items Needed:


    Deep Six HydrometerSalt does not leave the aquarium water when evaporation occurs. Over time, as the water evaporates, the salinity will increase. So you must monitor the salinity level of the water using either a salinity refractometer, or a hydrometer. Make sure the specific gravity is between 1.020 to 1.024 for most salt water fish only aquariums. If the salinity is too high, add fresh RO/DI water until the salinity is within the desired range. If you are making your own salt water, be sure to use RO/DI water to start with, then add your salt mix. It is best to mix the entire salt mix pack in the volume indicated on the package. So if the bag, bucket or box of slat mix you buy makes 55 gallons of salt water, mix the entire package in 55 gallons of water. This will ensure even distribution of materials in the salt mix when combined with the water. Also, make sure the new salt water has been thoroughly mixed for at least 24 hours and brought up to the proper temperature before adding it to your aquarium.


    Lifegard Aquatics Big Temp-Alert Digital Aquarium ThermometerMonitoring temperature is critically important for any salt water aquarium, so you will need a good thermometer. You want to make sure your water is at 78°F, higher than 80°F and your oxygen levels will drop which is not good for the fishes health. Below 74°F and it's starting to get too cold for your fish. If you find that you are struggling to get the temperature below 80°F you may need to add a chiller to your aquarium, or use fans blowing across the water surface to help keep the water cool using evaporative cooling. If you are having difficulty getting the temperature higher, you most likely need a bigger heater or an additional heater.

    pH and Alkalinity:

    Seachem MultiTest pH & Alkalinity Test Kit Marine & High pH Freshwater 75 TestspH is a measure of acidity verses alkalinity and pH will fluctuate in your aquarium daily. It is critically important to monitor and try to stabilize pH as best as possible. Typically you want to have your salt water in a optimum pH value between 8.2 and 8.5. Alkalinity works in conjunction with pH and should be in a range of 7° to 10° dKH, in order for the pH to remain stable. Adding powder or liquid alkalinity buffers, or frequent water changes will help maintain alkalinity, which also will help maintain stable pH.

    Ammonia and Nitrite:

    Red Sea MCP Marine Care Test KitGood salt water chemistry is important in any marine aquarium. After the nitrogen cycle is complete, you should not have any ammonia or nitrite left in the water. If a pump or filter fails, then you may encounter ammonia and nitrite spikes, which can be fatal to marine fish. If this happens you will need to do a large volume water change until the ammonia and nitrite levels are acceptable, then repair or replace the pump / filter as needed.

    Nitrate and Phosphate:

    Aquarium Pharmaceuticals Saltwater Liquid Master Test KitNitrates and phosphates require an ongoing treatment in a marine aquarium. If present in very high levels, they are dangerous to fish. They are also fuel for algae and can trigger an unwanted algae bloom in your tank. To avoid this, you want to keep the nitrate and phosphate levels as low as possible. Using nitrate and phosphate absorption resins are a good way to keep these levels low. We also recommend weekly partial water changes, gravel cleaning, and mindful feeding schedules so as not to over feed the tank, thus taxing the bio-capacity of your system.

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