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Old 06-29-2021, 01:05 PM   #1
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Hello everyone! (help needed)

Hi everyone!

I recently started looking after a female goldfish (Grogu) whose previous owner couldn't continue looking after.

Unfortunately, for the past 2-3 weeks I've only been able to keep her in a small 20L fish tank (a 35L fish tank is on its way but I'm afraid that's as large as it can be due to lack of space).
  • https://imgur.com/a/JxZmC4f

I am new to fish keeping so I started reading about the nitrogen cycle and the "new aquarium syndrome". Unfortunately, I'm struggling to balance the aquarium. Here is my process:

Fill in the 20L tank with tap water. I add Tetra AquaSafe product and a 1.5L bottle of distilled water and 5ml of Tetra FilterActive Bacteria.

The water filtering is done through a sponge filter (2W), which size is the recommended for this tank size. The plant is artificial.

Every 2-3 days I do a 30-50% water change (depending on how bad the water test results are).

Tank after 2 week of water cycling (pictures taken immediately after a 50% water change ):


After 2-3 days from the last water change I observe:

The Ammonia levels (tested with API ammonia test strips) is zero. I understand this means the bacteria that turn Ammonia into Nitrite are doing their job.

The Nitrite levels spike after 2-3 days to dangerous levels (>1ppm).

The Nitrate levels remain 20-30ppm.

The issue appears to be the lack of bacteria that would turn the Nitrite into Nitrate. Also, the presence of brown algae (diatoms?) concerns me as well.


Should I continue water cycling the tank? Will the Nitrite eventually stabilize?

With each water change, should I continue to add the Tetra FilterActive product?

Should I clean the brown algae (diatoms?) from the pebbles and plants? are they dangerous?

When the Nitrite levels get dangerously high, I've tried using Seachem Prime Concentrated Conditioner with little success.

Thank you very much for all your help in advance !


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Old 06-29-2021, 01:19 PM   #2
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Welcome aboard. We are glad you found us here at AA.


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Old 06-30-2021, 02:19 PM   #3
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Your goldfish Grogu is absolutely adorable! I like the Mandalorian as well
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Old 07-05-2021, 12:30 PM   #4
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It's nice you have taken on a project to help this fish. Goldfish are wonderful pets and friends. But they definitely can cause lots of water parameter issues. Especially at the beginning of a cycle and in a small tank.

Changing water to keep the fish in a safe environment is critical. A fish in cycle can last many weeks as it takes awhile for beneficial bacterial to establish number enough to handle a big GF in a small tank in your case.

20 liters is approximately 5ish gallons.
35 liters is around 9.25G

Still very tiny of a space for a GF. 20G or appx. 76L would be a good size.

That said, some keepers, likely with very much experience have kept fish into tens of years in smallish containers.

There is always the need for the GF to have very good water conditions and that is the fact.

When they do not have good water quality, they suffer internal damage which you can not always see, and external damage which usually means the internal damage likely already occurred. NitrIte and ammonia poisoning.

They get stressed and can loose out on higher amount of immunity resistance their body would normally have.

Your tank will cycle over time. #1 thing is not to wash the filter in chlorinated water, and not too harsh of scrubbing on it when you do.

The article link in my signature is quite a bit of help for new fish keepers. You likely have read about a lot of it though it is nice to be able to go back to it for clarification and reinforcing info.



The Diatoms build their shels from silicates in the water. You can leave the light off in your aquarium, most of the time, block direct sunlight if it comes in and hits the tank, and you can use a silicate binder product. Like Seachem Phosguard or Purigen.

I saw this thread a long time ago and was amazed by it, and try to share it with new GF keepers
New to FW fish? First tank in a long time or EVER??? Need some info on keeping fish?

Start here - Aquarium Advice Article

FW Favorites right now Clown Loaches, any shrimp - SW Vase Red Mangroves
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