Cycling a shrimp tank: how long and how to tell

The short answer

Cycling means growing the bacteria that turn ammonia into nitrite and then into nitrate. Ammonia and nitrite are harmful to shrimp, so you want that bacteria in place before the first shrimp arrives. A new tank also has little biofilm for shrimp to graze on, so patience helps them as well.

Step by step

1. Set up and treat the water

Fill the tank with treated water. San Diego tap is chloraminated, so use a conditioner that neutralizes chloramine. For Caridina, use remineralized RO water mixed to the tank’s target TDS instead, and add the active soil before you fill.

2. Run the filter and add live plants

Start a gentle sponge filter and add plants or moss. Plants and surfaces give bacteria and biofilm somewhere to grow, and they take up some of the ammonia.

3. Add a small ammonia source

Beneficial bacteria need ammonia to feed on. Drop in a few flakes of fish food or a small dose of a bottled ammonia product made for cycling, and follow the label. Do not add shrimp to supply it.

4. Test every few days

Use a liquid test kit for ammonia, nitrite and nitrate. Test-strip results are rougher and easier to misread. Write the numbers down so you can see the trend.

5. Wait until ammonia and nitrite clear

The cycle is working when ammonia rises and falls, then nitrite rises and falls, and nitrate begins to show. It is done when a fresh small dose of ammonia reads zero ammonia and zero nitrite a day later.

6. Do a water change, then add shrimp slowly

A modest water change brings nitrate down and checks that your water matches. Then add a few shrimp first, drip acclimate them, and watch for a week before adding more.

Neocaridina and Caridina

Neocaridina are the forgiving choice and do well in dechlorinated San Diego tap water, so their cycle is the simpler one. Caridina need soft, acidic, low-TDS water, and active soil releases ammonia in its first weeks, so expect a longer cycle and test more often. See water parameters and San Diego tap water for shrimp for the numbers.

Ways to speed it up

Seed the tank with a squeezed-out piece of sponge, filter media or plants from a healthy established tank that has not been treated with copper or other invertebrate-unsafe medications. Moss and plants help a new tank settle. Even then, rely on your test results rather than the calendar.

Questions we get asked

How long does it take to cycle a shrimp tank?

Plan on about four weeks for a Neocaridina tank and six to eight weeks for Caridina on active soil, which also releases ammonia early on. A tank seeded with mature sponge or media from a healthy established tank can be faster, but test rather than guess.

Do shrimp tanks need to be cycled?

Yes. Shrimp are sensitive to ammonia and nitrite, and a new tank has no bacteria to remove them and little biofilm to graze on. A tank can test clean and still be too young, which is why shrimp added early often thin out over the first month.

Can I add shrimp while the tank is still cycling?

No. Ammonia and nitrite rise during a cycle, and both are harmful to shrimp. Wait until both read zero and nitrate has appeared, then add a few shrimp and acclimate them slowly.

Why does my test show ammonia after I dosed the water conditioner?

Some conditioners that neutralize chloramine temporarily bind the ammonia they release, and some test kits can still read it. Check the conditioner label and your kit’s instructions, and judge the trend over several tests rather than one reading.

Is it a problem if ammonia stays above zero for weeks?

It can be normal early in a cycle, especially with active soil. Stop adding ammonia, make small water changes if the reading is high, and keep testing. If it does not fall after several weeks, check that the filter is running and the water has been conditioned.

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