Saltwater Fish Care

Written and verified by the biologist Cesar Paul Gonzalez Gonzalez

Written by Cesar Paul Gonzalez Gonzalez

Last update: 21 December, 2022

Fish are animals with a great diversity of shapes, appearances, and sizes, which is why they’re so popular in people’s homes. In fact, marine species are the most colorful, which is why saltwater aquariums are often the preferred option. However, because the conditions in the sea are very stable, looking after saltwater fish is usually more complicated.

For this reason, this article will list the main recommendations, as well as everything you should take into account before entering the world of fish keeping. Continue reading to learn more about this topic.

Saltwater fish

Saltwater species are more expensive than freshwater ones, because most of them have very strict requirements for their maintenance or reproduction. In addition, some of them are captured in their natural habitat, which increases their cost and scarcity.

One of the best recommendations is to start with easy specimens, as they can cope with water changes a little more. In addition, it should also be noted that they’ll need an artificial ecosystem that resembles their natural environment as closely as possible. This could involve adding invertebrates such as corals or anemones, to complete the appearance and functionality of the tank.

Saltwater fish with simple care

With this clarified, we propose some types of fish that could be good choices to start your aquarium:

• Clownfish: This is one of the most popular specimens because of the famous Pixar / Disney children’s movies. Captive-bred varieties are very resistant and colorful, however, they will need the presence of anemones, and in general a coral reef type environment.
• Damselfish: This is one of the most colorful species on the market. Its tank must have coral reef characteristics, as they’re closely associated with this species. In fact, it’s a good companion of clownfish and different types of gobies.
• Green damselfish: The best choice if you want to keep a coral reef aquarium, as they’re easy to breed and adapt well to almost any food. The only problem is that they’re guild specimens, so you’ll have to add them in groups.
• Banggai cardinalfish: A species that is usually peaceful and shy, but needs oxygenated water and hiding places for shelter. Most of these specimens do not represent a problem in captivity, but depending on where they are acquired, they may or may not be accustomed to eating processed food.
• Bicolor blenny (Ecsenius bicolor): This animal can adapt to tanks with few species, and can even cope with being the only one in the aquarium. However, it needs live rock for food and shelter. It’s a shy but sociable fish, which needs to have enough space, as it gets easily stressed if it can’t swim freely.
• Yellow coral goby and fire goby: Both fish are considered reef fish, so they’ll need coral in their environment. Due to the territoriality they show towards their own species, it’s best to keep a single specimen or breeding pairs.
• Royal Gramma: This colorful fish should only be kept in fairly large tanks, as it becomes aggressive in small aquariums. In general, its behavior is peaceful, but it can cause territorial problems with other individuals of its species.

These are just a few examples of fish you can have in your aquarium. Also, remember that the best option is to choose those that come from hatcheries, as they’re more accustomed to life in a tank.

The saltwater fish tank

Sea fish are some of the most beautiful species in the world, and their bright colors, sizes, and peculiar shapes, make them very popular as pets. Despite this, conditions in the sea are different from those in freshwater, since saltwater doesn’t have significant fluctuations in its chemical parameters.

Because of this, saltwater aquariums must maintain precise control of conditions to ensure the quality of life of the fish that inhabit them. This means that it’s important to invest time, space and money to get the tank ready before the fish are introduced.

Tank criteria

To begin with, aquariums need ample space for each specimen to swim freely. This means that the minimum tank size should be 300 liters (65 gallons), but one larger than 500 liters (110 gallons)  is recommended when you aim to have several specimens. In addition, it should have a depth of 60 centimeters (24 inches), as this will allow you to create areas with different amounts of light.

In addition, decoration is very important, as this will allow your pets to feel calm and safe. With this in mind, ornamental rocks and live rocks need to be placed to provide caves or nooks and crannies to serve as hiding places. Moreover, this will make it easier to keep your aquarium stable, as they allow the formation of bacteria and algae that will maintain the health of the tank environment.

On the other hand, as for the substrate, a good option is to use sand and coral, which will fill the bottom with at least 2 millimeters. In fact, the latter will depend on the species you want to have, as some require a larger amount of substrate, such as gobies, for example.

Recommended equipment

As mentioned before, saltwater aquariums must be monitored accurately, as their parameters shouldn’t vary suddenly. For this reason, a large part of the initial expense for the tank is for the equipment you need to carry out the measurement and maintenance of water quality. In this regard, the following equipment is recommended:

• LED light: Light is critical in order to maintain the growth of algae and vegetation in the aquarium. Moreover, there must be a balance between white light and blue light in order to have a balanced system.
• Tank filter: There are many different options, which will depend on the needs of each aquarium and species. For hardy fish, a biological filter is more than enough. However, when you intend to keep other more sensitive species, it’s better to additionally opt for a skimmer that filters and regulates ammonia better.
• Activated carbon filter: This is additional and should only be considered when keeping a multi-fish system. However, it also serves to maintain the balance in the tank.
• Recirculation pumps: Even if you think they aren’t necessary, these pumps help improve oxygenation and create currents that mix the water and balance the parameters. This is often necessary for the care of various saltwater fish.
• Reverse osmosis system: Recommended, but not essential, it helps to purify the water to carry out replacements. This mechanism facilitates the process, but can be done at home if you don’t have the budget.
• Densimeter: The most important part of a saltwater aquarium is the correct concentration of salt in the water, and, with this tool, you can measure the salinity and prevent it from exceeding optimum levels. An alternative is to use a refractometer that uses another process to measure the concentration, but fulfills the same objective.
• Heater (cooler): Because they’re tropical water species, the temperature must be kept stable, so a thermostat can save your fish’s life.

Water parameters

With regard to the usual water parameters, the needs of each species should be taken into account, but, in general, the following criteria can be used:

• Temperature: 24-26 °C
• Specific gravity (salinity): 1.025
• pH: 8.0-8.3
• Ammonium: 0 ppm
• Nitrites: 0 ppm
• Nitrates: < 10 ppm
• Alkalinity: 6- 9° dH
• Calcium: 400- 450 ppm
• Magnesium: 1200-1320 ppm
• Phosphates: 0 ppm
• Iodine: 0.5-0.8 ppm
• Iron: 0.1-0.3 ppm

Water cycling and first set-up

When the aquarium is set up for the first time it’s necessary to perform a cycling procedure to “mature” the tank and achieve stability. This is accomplished by running it for a period of time with only water and decorations. During this process, the parameters are monitored to check how much they vary.

In the first week of cycling, it’s recommended to add live rock so that the bacteria will help the maturation. In addition, small portions of food should also be added to help microorganisms grow in the aquarium. The infallible sign that determines the maturity of a tank is the presence of nitrates, but not nitrites, so this should be checked with measuring kits.

The process can take 6 to 7 weeks, so it should be prepared in advance, to receive the new fish at the right time.

Salt water replacement and preparation

To keep the aquarium system stable, it’s recommended to change 20 to 30% of the water every week. This procedure should be carried out in a clean container that’s free of any chemicals or impurities. In this container, osmosis water or distilled water is added, in addition to 35 grams (1.4 oz) of synthetic aquarium salt.

At this point, it’s necessary to stir the water and measure its chemical parameters. However, this should be done with the water at a temperature of 25-26 degrees Celsius, as this may change the result of the measurements. Once confirmed to have the correct salinity, this water is ready for replacement.

The replacement process should be slow, gradually removing the water from the tank and replacing it almost immediately with new water. Remember to check the parameters of the tank, to confirm that the water quality is stable.

Preliminary care of saltwater fish

As with the aquarium, the fish must go through a process of acclimatization that allows the specimens to adapt to their new home. To do this, it’s necessary to follow a series of simple steps that will allow you to avoid stressing your new pet.

The first thing to do is to use the bag or container that was given to you and put it, without opening it, inside the tank for 30 minutes. This is done to ensure that the temperature of both waters is equalized and the fish doesn’t suffer a thermal shock. After that, the bag is opened, and without releasing it, it’s combined with the water in the tank, slowly, and in small quantities.

After a few minutes, the process is finished, and our pet is released into its new home. Remember that it’s best to turn off the light and perform all these steps as slowly and gently as possible.

Care of saltwater fish in the aquarium

Once the fish are installed in the aquarium, you only need to check two things, their diet and their health. For the first point, it’s necessary to verify the nutritional requirements of each species, in order to know what kind of food to give them and how many times a day. In general, a balanced diet between live and processed food is usually suggested.

Regarding the second point, most health problems are caused by poor water quality. Among the most common diseases are velvet skin, caused by a dinoflagellate, and marine ich, a ciliate infection. Both pathologies are evidenced by a change in the fish’s skin, so it’s necessary to be aware of any anomaly.

In most cases, the medication must be administered directly into the water, which is why it’s preferable to have an extra tank in the form of a “hospital”. With this, it is possible to avoid the contagion of the other specimens you can carry out a better follow-up to favor the fish’s recovery.

Everything we’ve mentioned will incur a lot of expense and time, but it’s all very worthwhile. Owning a pet isn’t something you should take lightly, as the animals depend on us for their well-being. However, the greatest reward is the opportunity to be so close to beautiful and enigmatic species like these saltwater fish.