Choosing substrate for a shrimp tank

The short answer

Substrate affects shrimp in two ways. It gives them a surface to graze and hide on, and some kinds change the water chemistry. Knowing which kind you are buying is the whole decision.

Inert substrate

Inert gravel and sand do not change pH or hardness. That suits Neocaridina, which tolerate dechlorinated San Diego tap water, see Neocaridina. Pick smooth, aquarium-safe material. Dark colours show off cherry and Blue Dream shrimp, while very coarse or sharp gravel is harder for tiny shrimplets to move through. Rinse it well before use, and add it before filling the tank as described in shrimp tank setup.

Active soil

Active substrate, usually sold as aquarium soil, is designed to lower pH and soak up carbonate hardness. It is mostly used with Caridina, which need soft, acidic water. Our tap water is hard and alkaline, so Caridina keepers typically blend in low-TDS water rather than relying on soil alone, see San Diego tap water and water parameters.

Soil does not last forever. Its buffering fades as it takes up minerals, so test the water regularly and plan on replacing it eventually. Fresh soil can also release ammonia early on, which is another reason to cycle the tank before adding shrimp.

What to avoid

Skip anything not made for aquariums, including potting mixes with fertilizer or pesticides, and avoid material that is not labelled safe for fresh water, since it can change hardness unpredictably. Do not add copper-based products to the tank, see medications and copper.

Questions we get asked

What is the best substrate for Neocaridina?

Any inert gravel or sand works well. Neocaridina tolerate our hard tap water, so they do not need buffering soil. Many keepers choose a dark colour because it makes shrimp colours stand out.

What is active substrate?

Active substrate, often sold as aquarium soil, is made to lower pH and buffer carbonate hardness. It is mainly used for Caridina, which need soft, acidic water. Inert substrate leaves the water chemistry alone.

Can I use active soil with San Diego tap water?

Not on its own for Caridina. Our tap water is hard and alkaline, so Caridina keepers normally mix in low-TDS water such as reverse osmosis. Soil alone is unlikely to hold the right conditions with straight tap water.

How long does active substrate last?

Its buffering fades over time as it takes up minerals, commonly after many months to a year or more depending on the water. Test regularly and expect to replace it eventually.

Is sand or gravel better for shrimp?

Both are fine. Fine sand packs tightly and shows debris, while small gravel leaves gaps for shrimplets to hide. Choose smooth, aquarium-safe material either way.

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