20 Gallon Tank Cycling A New 20 gallon Tank for snails and Betta Splendens

Hi everyone,
I am setting up a new 20 gallon tank for snails and a Betta Splenda. Any suggestions will be great for plants. Over a month and half of fish-less cycling now. I am testing my tank water with API liquid test kits. Finally last week, ammonia levels went to 0 ppm, with nitrite at 0 ppm and nitrate at 5 ppm. I dosed with Ace branded ammonia to 4ppm. After 96 hours, my ammonia-oxidizing bacteria reduced the ammonia levels down to 0.25 ppm, nitrite was 0 ppm and nitrate was at 10 ppm. Will dose again when ammonia level is at 0.0. Will keep everyone updated.

Answering the Template:
Tank
What is the water volume of the tank?:
20 gallons
What type of water are you using in your tank? (tap, well, RO/DI, other):
Tap water treated with Seachem Prime water conditioner
When did you start cycling the tank?:
15 August 2026
What type of filtration are you running on this tank? (sponge, HOB, canister, other):
two sponge filters, one DIY sponge filter, and HOB (with manufactured cartridge, and sponge media)
Do you have good water agitation/surface movement?:
I have an air stone and light with air bubble strip plus the HOB, this creates plenty of agitation and surface movement.
What is the water temperature?:
Water temprature is 80 deg F
PH is 7.6
KH is 107.4 ppm
GH is 70 ppm

Color Guessing game
API Freshwater Master Kit
Ammonia test:
1? 1.5? 2? ppm
This is after 25 hours of dosing to 4ppm using 180 drops of Ace Hardware branded house ammonia.

Not an expert here, but I've been staring at that exact same color situation in my own tanks, so here's what helped me.
That awkward "is it 1 or 2" moment happens because the liquid test kit only gives you printed reference swatches, and between two of them you're just eyeballing. A few things that make the reading a lot more repeatable:
- Hold the vial flat against the white color card with the same background every time — a white piece of paper behind the vial beats a busy countertop.
- Use daylight from a window, not the tank light or a warm bulb. Artificial light shifts that green/yellow ammonia color more than you'd expect.
- Take a photo of the vial next to the card at the same time each day. Comparing yesterday's photo to today's vial is honestly easier than trusting your memory of yesterday.
- If it lands between two swatches, just log it as "between 1 and 2" and move on. The trend across days matters way more than nailing the exact number.
Now the part I'd actually celebrate: you dosed to 4 ppm and 25 hours later you're reading somewhere around 1-2. That means the bacteria in that tank chewed through roughly half the dose in a day. That's not a stalled cycle at all — that's a colony that's actively working. On my first tank I was stuck seeing the full dose sit there untouched for days, so seeing numbers move like yours is a good sign.
The thing to watch next is nitrite. When ammonia starts dropping this fast, the second group of bacteria usually lags behind and nitrite climbs hard for a while. The finish line I've seen people describe here is dosing and getting both ammonia and nitrite back to 0 within about 24 hours. Until then, once ammonia hits 0 again, re-dose so the nitrite eaters keep getting fed.
One question that would help you read where you are: at that same 25-hour mark, what are your nitrite and nitrate vials showing? If nitrate is already climbing while ammonia falls, your cycle is further along than the ammonia number alone suggests.

One question that would help you read where you are: at that same 25-hour mark, what are your nitrite and nitrate vials showing? If nitrate is already climbing while ammonia falls, your cycle is further along than the ammonia number alone suggests.

Click to expand...

Thank you for you reply yulongtang! Your tips are great. I changed my daily water test to 4pm in the afternoon so I had natural light versus at night before bed. To answer your question: At the 25 hour mark, I did a nitrite test and it was 0 ppm. Nitrate was 20 ppm before dosing.

I started the cycling process on 15 August 2026, so tomorrow it will be 2 months, no added old media or any store bought bacteria in a bottle. I am enjoying the long slow process for it helps my mental well-being. Once my tank is truly cycled, I will then go and splurge on plants and get them growing. Then one nerite snail and finally the right Betta Splendens fish.

Friends and family already asks what are you going to get for your tank etc. and I grin and say well right now I am growing some lovely Nitrosomonas!

Update: VERY Low PH and KH

During my fish-less cycling, I noticed that my tank's water PH was 6.0 or lower and KH was 1 dKH or lower. After reading several websites, it worried me that this may stall my cycling (see 1st pix). After perusing several sources on how to raise PH, I decided to use Baking Soda. Over the course of 2 hours I dosed my tank with 3 teaspoons or 15g of baking soda dissolved in tank water. after 25 hours, PH in my tank water rose to 8.2 with KH testing at 8 dKH (see 2nd pix).

The overly high PH bothered me. Several sources reassured me that the higher PH will not affect my cycling. I learned about the acidification of my tank water as a result of nitrosomonas adding hydrogen into my tank as a part of the nitrogen cycle.

I got curious and tested my source tap water after letting it sit and aerate for 20 hours. My source tap water has a PH of 6.8, a KH that varies between 1-2 dKH, and nitrate reading of 10 ppm (see 3rd pix). Now I am concerned that my source water will not have enough dKH and is too low in PH for my planned tank. After reading some more sources, crushed coral seemed to be the answer to increase KH and thereby stablizing PH. However, I have no room in my HOB filter for the crushed coral. One source even said some oyster shells might help. I've got some bleached oyster shells that I can use as decoration!

Question:
Is adding crushed coral mixed in with substrate, and floating plants the best solution to increase KH and decrease nitrate in my tank?

After increasing the PH and KH, my cycling continued to progress. Here are the numbers today, 17 October 2026, at 4pm and 121 hours after dosing tank water to 4ppm:

Temp = 77 F
PH = 7.6
KH = 7 dKH
Ammonia = 0.0 ppm
Nitrite = 0.0 ppm
Nitrate = 100 ppm
(see 4th pix)

So I dosed the tank up to 4ppm with pure ammonia to allow the tank to cycle once more.

I have low KH also, and I put some crushed coral into a media bag and put the bag into my canister filter. Mixing the crushed coral in with the substrate is fine also, but it would be hard to remove if you put in too much. You could just put crushed coral into a media bag and put the bag right into your tank.

I have low KH also, and I put some crushed coral into a media bag and put the bag into my canister filter. Mixing the crushed coral in with the substrate is fine also, but it would be hard to remove if you put in too much. You could just put crushed coral into a media bag and put the bag right into your tank.

Click to expand...

Thank you jdhef. I went to my closest lfs, and they did not have crushed corals, but they did have cuttlefish bone. So I boiled two and placed one in my HOB filter and another into a mesh bag already hold my ceramic media. I also placed 5 cleaned oyster shells on to the bottom of my tank. Hopefully, this will keep my KH higher than my tap water. Will keep y'all up-to-date!

Hi everyone! GREAT NEWS.
Today, 20 October 2026, at 5:03pm I tested my water parameters. After 24 hours of dosing to 4ppm my Skyquarium showed: Temp 77 F, PH = 7.5, KH = 6 dKH, Ammonia = 0.0 ppm, Nitrite = 0.0 ppm, nitrate = 5-10 ppm, TDS = 246 = GH 13.74.
(Whispering)
Might my tank be cycled ?!
I dosed up to 4ppm with pure ammonia at 5:30pm.

I added a Anubias Bateri, and two small Spider plants to the tank setup and in 24 hours the nitrate went down. Looks like this weekend will be a time for water change, snail and Betta Splendens rescue from Petco! Now will read up on drip acclimatization. It seems the old bag in the tank for 30 minutes is no longer best practices....

Thank you to all for your help and support on this long, challenging but enjoyable process.

A tiny little bug fell into Skyquarium around 11pm last night. I wish my future Betta Splendens was there to snake on it. Instead it drowned and caused a minor increase < or = 0.25 ppm in ammonia this morning...

Yesterday 31 Oct 2026, I rescued Sky Draconis-Squāma from my LFS. Sky showed his hunger by attempting to eat small bits of crushed coral and plant particles on the bottom of the tank. Sky devoured a large meal (1 pre-soaked pellet, 3 dried Daphnia). This morning he greeted me by blowing bubbles on the surface of the water ! At 8am, test result returned a 0.25 ppm ammonia . I immediately began a 50% water change with de-chlorinated and heated water.
Sky is happy and active, nipping at the plant detritus kicked up by the water change and chasing after the bubbles from the waterfall off of the HOB filter.

It came in LFS water that contained 0.50 ppm ammonia and was at or below 6.0 PH...

20 Gallon Tank
Temp = 78 F
PH = 7.2
KH = 2 dKH
Ammonia = 0.25 ppm
Nitrite = 0.0 ppm
Nitrate = 10 ppm

Followed jdhef 's advice and now there is 3/4 lbs of crushed coral mostly in the aquarium and some in the HOB filter.

After 50% water change ammonia was brought to 0.0 ppm.

Hoped to avoid in-fish cycling, will monitor ammonia levels twice a day and do water changes when necessary. Stand by for further updates!

Okay, the water change yesterday morning did the trick! This morning water condition and parameters are now normal! More importantly, Sky Draconis-Squāma is thriving Here are the latest results:

Temp = 78 F
PH = 7.2
KH = 2 dKH
Ammonia = 0.0 ppm
Nitrite = 0.0 ppm
Nitrate = 10 ppm

Back to being a cycled tank. Thank you Fishlorians!

Happy to report the crushed coral is working. The tank has a consistent dKH and dGH of 4-5.

Recently, I got a sporadic 0.25 ppm ammonia reading. I over fed my fish and a pellet and a few freeze-dried daphnia that my fish did not finish caused the increase. Dis a 10% water change and all is normal.