To expand on what
@minorhero said, he’s MOSTLY correct. There are only 2 things I might add.
- While beneficial bacteria do exist all over, they won’t multiply and colonize your filter without food (ammonia). This feels like a catch-22… you won’t have any beneficial bacteria without ammonia, you won’t have ammonia without fish, and you can’t have fish without beneficial bacteria. There are two solutions. One is outlined in the link I gave above, and that’s to add 1 hardy fish. Check the water daily, and any time there’s enough ammonia for it to register on a test, then change half the water. The lone fish is producing enough ammonia to start feeding bacteria, but not enough to kill it overnight. I’ll outline the second method below.
- You didn’t mention it in your original post, but you need to have a filter in your tank to hold biological media. This is usually a type of coarse sponge (good) or ceramic media (better). Do some reading on how to clean your filter, because it’s important. This may seem counter-intuitive, but cleaning your filter can kill your fish. This is where your beneficial bacteria lives, and tap water can contain chlorine, which will kill that bacteria.
On to how to do a fishless cycle…
Here are the things you’re going to need:
- Dechlorinated water- this means that if you are using tap water, you need to make it safe for your tank. Most pet stores sell products that “make tap water safe”. Look for these products, and add them per the instructions whenever you add water.
- A working filter of some kind- Bigger is better. Nobody has ever gone wrong by having too much filter media
- Household Ammonia- This needs to be completely free of anything else… No soaps, dyes, surfactants, or anything else. Usually sold at home improvement stores, and comes in strengths of 5-10%
- Water test kits. You need to have tests for Ammonia, Nitrite, and Nitrate
Step 1: Ensure filter is running, has media in it, and you’re using dechlorinated water. Test your water for ammonia , nitrite , and nitrate . You should have 0 ammonia and nitrite, and <5 nitrate
Step 2: Use this calculator to determine how much ammonia you need to add to get to 2ppm in your water column. I entered 10% strength ammonia for this example, but if you use something else, just use this calculator. Again, you’re aiming for 2ppm ammonia. For your tank size, assuming 10% ammonia, you would be adding 1.4mL of ammonia. The easiest way to measure this would be to add 10mL to 100mL of water, then add 14mL of that mixture.
Ammonia Calculator for Aquariums - Spec-Tanks (spec-tanks.com)
Step 3: Let your tank run like this, and check for ammonia, nitrite, and nitrate every day. Don’t add any more ammonia just yet
Step 4: When your ammonia begins to decrease, you should see nitrites begin to increase. This is displaying growth in beneficial bacteria
Step 5: If at any time your test shows 0 ammonia, dose it again to 2ppm like in step 2. Repeat this step whenever you test your tank, and read 0 ammonia
Step 6: If at any time your test shows >= 5ppm Nitrite, do a 50% water change. Check for ammonia again and dose if needed (step 5)
Step 7: By this point, you should be seeing Nitrates in your test. If at any point, your nitrates are >=40ppm, do a 50% water change. Check for ammonia again and dose if needed (step 5)
Step 8: You will hit a point where you dose 2ppm ammonia, and your bacterial will convert all of it to Nitrite AND to nitrate in 1 day. If you dose 2ppm of ammonia today, and you have 0 ammonia and 0 nitrite in your tank at the same time tomorrow, then your tank is fully cycled.
Step 9: Once your tank is fully cycled, it is almost ready for fish. The last thing you’re going to want to do is a massive (90%+) water change to remove all of the nitrates you created. Do this the day before you plan on adding fish.
Notes: These are super important.
- During this whole time, do not touch your filter, and do not let it turn off.
- During every water change, make sure you are adding water dechlorinator to the tank before you add the tap water (drain tank -> add dechlor -> refill tank)
- If things feel like they have stalled at any point, you can add bottled bacteria to give you a jump start. There are several brands out there, but I’ll leave it to others for recommendations. I’ve never used them.
