New Year, New Tank, Freshwater, Brackish Water or Saltwater?

Learn as much as you can by comparing the similarities and differences of the aquarium types.

White-bonnet anemonefish. ( Amphiprion leucokranos. Via Michael McComb/Flickr

Tina is an accomplished aquarist who learned the art and science of fish keeping over the past two years. She currently has a 76 liter (20-gallon) freshwater community tank. Now that Tina has mastered the intricacies of her fish-only tank, she is ready to take on another aquarium challenge.  Given that she is well ‘grounded’ in aquarium husbandry, Tina is considering a freshwater planted tank or a saltwater reef tank. She has been told saltwater tanks are very expensive, difficult to keep and scientific. Tina learns, depending who she talks with, that compelling arguments can be made for any of three types of aquariums: Freshwater, Brackish Water and Saltwater. Tina decides to learn as much as she can by comparing the similarities and differences of the aquariums.

It is difficult to compete with the beauty of saltwater species. Photo by Stephen G. Noble.

Freshwater, Saltwater, and Brackish Tank Similarities

  1. Virtually anyone can keep either a freshwater, brackish water or saltwater aquarium if they have the correct information and dedication to succeed.  The level of effort to maintain a pristine tank depends on the sophistication of the set-up.  You don’t need to be a scientist to keep an aquarium.  But, a basic understanding of chemistry will certainly help.
  2. Generally speaking, a tank, stand, substrate, filtration, lighting, water parameter testing equipment, food and ancillary items such as scrapers and nets are required for any aquarium.
  3. One might think saltwater aquariums are the most expensive but this may not be the case. The equipment costs for each type can be about the same.  For example, a high technology (high tech), freshwater planted aquarium with plant-specific substrate, special lighting, CO2 injection system, testing equipment and plant fertilizers can easily cost as much or more that a comparatively sized saltwater tank.
  4. They all need to have a fully established nitrogen cycle. New Tank Syndrome (NTS) is the leading cause of fish mortality in all types of aquariums.
  5. Routine maintenance such as conducting partial water exchanges and filtration maintenance is necessary for all aquariums.
  6. A higher bioload (all living organisms) means more maintenance regardless of the type of aquarium.

Brackish water tanks are ideal for transitioning to saltwater tanks. Photo by Stephen G. Noble.

Freshwater, Saltwater, and Brackish Tank Differences:

  1. Freshwater partial water changes are easier to conduct than brackish or saltwater.  Normally, freshwater partial water changes only require the water to be treated for chlorine and chloramines.  Two additional steps are required during partial water changes for salt and brackish water.  They are the mixing of salt into the replacement water and verifying with a hydrometer the specific gravity (salt contentment).
  2. Most freshwater and brackish water fishes are more adaptable than saltwater fishes to variations of their water chemistry.  In the wild, seasonal rains and floods alter the water temperature, pH, hardness and total dissolved solids, making freshwater and brackish water species very resilient to change.  However, saltwater fishes are considerably less tolerant to variations of their water chemistry.  The reason being that ocean reef water chemistry is very constant with only slight, daily pH and temperature fluctuations.  Therefore, saltwater fishes are best kept in a narrow range of pH (7.8-8.4) and a specific gravity of 1.020-1.025 for FOWLR (Fish Only With Live Rock) tanks and 1.023-1.025 for reef tanks.   Freshwater and brackish water species are more tolerant to degraded water conditions if routine maintenance is deferred for a few days; assuming the tank is not overstocked.  This is not the case with a saltwater aquarium where deferring maintenance can quickly result in stressed fish becoming susceptible to bacterial infections ending in death.  Saltwater tanks are not for procrastinators.
  3. Saltwater is capable of holding only about 80% of the oxygen as the same volume of freshwater.  Saltwater tanks must be stocked with a lower bioload than freshwater and brackish water tanks.
  4. Live plants greatly help freshwater and brackish water tanks maintain good water quality by consuming excess nutrients.  Live plants directly compete with algae for the same nutrients resulting in significantly less algae blooms in heavily planted freshwater and brackish water tanks.  Excessive algae growth can become a problem in saltwater tanks because there are no plants to compete for the excess nutrients.  The only way to combat algae and cyanobacteria (formerly called algae) in a saltwater tank is to conduct partial water changes, cleaning the protein skimmer and vacuuming the coral substrate.
  5. Up to now, one might think saltwater tanks require the highest level of maintenance.  But that notion is easily refuted if a saltwater tank is compared to a high tech freshwater planted aquarium.  Planted tanks can be extremely high maintenance requiring daily pruning and ‘primping’ making their maintenance requirements far in excess of an average saltwater tank.

Heavily planted freshwater tanks are underwater gardens. Photo by Stephen G. Noble.

A strong argument can be made for the benefits of transitioning from fresh to brackish water before attempting a saltwater tank.  Brackish water fishes are tremendously tolerant of water chemistry variations.  Because they are so hardy, these fishes are forgiving of minor mistakes when learning the proper way to mix and test salt water.  After careful consideration, Tina decided to try a 340 liter (90-gallon) brackish water Archerfish aquarium.  She is certain to enjoy exploring a new aspect of aquarium keeping.  Enjoy your fish!

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Freshwater Fish