Methods of Providing Calcium for Freshwater Invertebrates.

Methods of Providing Calcium for Freshwater Invertebrates.

A shrimp molt.
Calcium plays a vital role in any aquarium with invertebrates; they require a certain amount to maintain their shells or exoskeletons. This can be provided to them in a number of ways, and this article will outline some of the methods that aquarists can use.

Fish and plants will also benefit from a good level of calcium.

Please note that much of the information here, though based on evidence and experience, is still a matter of opinion. Good fishkeeping requires thorough research and each source may provide a different viewpoint.

Mineral Additives Designed For Shrimp & Snails

Many products have been designed to address mineral issues for aquarium inverts. Anyone with fish and shrimp have a variety of products to choose from. Be sure to dose the minerals according to the packaging; any more could result in water that's too hard, and you will have different parameters than intended. Always pre-mix the minerals with dechlorinated water as part of a water change, rather than adding it straight to the tank. This is because these minerals rapidly dissolve, and adding them straight in could cause osmotic shock in tank inhabitants.

These products are generally designed to only be used in reverse osmosis water. This means that it may cause problems if used in water that already has minerals; it could make the water too hard. Overall, this is a good all-round method for those who use RO water and want to cater for shrimp and snails. It is expensive however, and requires constant replacement.

Crushed Coral/Seashells

Possibly the most common way of adding calcium, or raising pH, GH and KH in general, is through adding crushed coral or seashells. This method is cheap, and crushed coral/seashells are readily available in pet shops or on beaches around the world. Note that anything from the beach or a waterway should be thoroughly soaked in hot water to prevent the introduction of parasites or other unwanted creatures. Crushed coral and/or seashells can be put anywhere in the tank, but the most practical place for them is in the filter. If the pieces are small enough, ensure they are secured in a non-watertight bag to prevent pieces getting stuck in the filter motor.

Crushed coral and seashells will dissolve overtime, and its dissolved particles will be removed via water changes. In lower pH conditions, they will dissolve noticeably quicker. When the majority of it has dissolved, replace it as necessary. Since calcium carbonate doesn't dissolve so readily in water, the pieces must be as small as possible to increase the rate it dissolves. In lower temperatures it will also dissolve slightly quicker.


Cuttlebone is another effective way of adding calcium to water. Simply wash a cuttlebone bought from a pet supply shop under warm water and throw it into the tank. Alternatively, cuttlebone can be easily be found at most saltwater beaches. Again, be sure to soak in hot water for a long time if using cuttlebone from the wild. After a few days the cuttlebone will get waterlogged and sink, allowing shrimp and snails to more easily eat from it, and for it to release calcium carbonate into the water.


Another common method of supplying calcium for inverts is by adding crushed eggshells. Crack open an egg, rinse it thoroughly under warm water, then remove the white membrane from the inside of the shell. Rinse again under warm water, then crush with a mortar and pestle. As with the seashells and coral, it's best to crush it as finely as possible, then add it to a bag that can pass water and put it in the filter. It will also need to be replaced.

Calcium Carbonate Pills/Antacid Pills

Calcium carbo
CC1542D3-4E3A-490B-8E81-E456BDA7E2DE.jpegnate pills can be used in snail and shrimp food, or dissolved into the water. Use a mortar and pestle to crush up the pills, then add them to a snail jello or shrimp food recipe, or add the powder directly into the water. Add roughly a large pinch per 10 gallons each week. Take care to use pills that don't have vitamin D, because too much vitamin D can be toxic to animals. If adding crushed pills straight to the aquarium, avoid flavoured ones because they may raise ammonia levels.


In all, these are just some of the ways to add calcium to a tank with shrimp, snails or other creatures. Other methods exist, but these are the methods I've personally used with success. If this article has helped you, please feel free to leave a rating and feedback. Thank you for reading :)
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