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I got a new 8 gallon (around 30 liters) fish tank on December 31st. And the same evening I put a 4 inch (10 cm) oranda and a 2 inch (5 cm) black moor in it. I totally forgot about cycling the tank. I even tried to return the fish back but they say they can't take the fish back.

Since yesterday, I've been searching the web for all similar issues and from there I learned that I need to do a weekly 10-15% water change to keep my ammonia levels in check, also I couldn't find a test kit anywhere nearby so I'm just observing the fish.

Tank Specifications

  • Volume: 8 gallons (around 30 liters)

  • Filter: 600 liters per hour

  • Filter media: 1 cm thick plastic sponge

  • Substrate: Medium size gravel (2.5 inch / 6.4 cm thick layer at the bottom)

  • Decorations: 3 plastic plants at one corner

  • Thermometer: submersible

  • Heater: not needed as my room temp is around 20 °C mostly

  • Lighting: built-in hood lights

  • Ammonia, nitrate, nitite: unknown

Black moor's behaviour:

The moor is sitting at the bottom every 5 minutes for about a minute or so and again starts moving again normally, searching for food.

Oranda's behaviour:

Oranda is behaving rather normally, but it's also tanking a break for a little while but with shorter durations.

Both of them get active at the feeding time (which looks normal) and are eating well. But, I know that they are having a hard time staying in there. I just want to know how long will my tank tank to cycle this way and if I need to do some other things.

Thanks.

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The first thing you need to do (since you did not mention this) is ensure that all water that enters your aquarium is dechlorinated. Chlorine is used to treat household water and although its levels are harmless to us, they are deadly for fish. You can dechlorinate your water by using one of the many dechlorinating kits that you can find either at a pet shop or online. If you did not dechlorinate the water, you need to do so immediately as your fish are practically swimming in acid, and chlorine will eventually damage their gills (and will most probably cause asphyxiation to them with fatal results).

A test kit is vital for monitoring the well being of your aquarium. You need to remember that by simply observing your fish you cannot know when your tank has cycled. By definition, a cycled tank is the one where zero ammonia and zero nitrites exist. Since fish tolerate low levels of ammonia and nitrites (at least on the short term) they will most probably not show any symptoms of stress or ammonia/nitrite poisoning. However, this does not mean that the tank has actually cycled.

Moreover, while a tank gets cycled the ammonia and nitrite levels fluctuate a lot. By using a test kit and doing proactive testing on your aquarium (say, once or twice a day) you will be able to identify rapidly rising ammonia and nitrite levels (called ammonia/nitrite spikes) and pro-actively perform water changes before their levels become dangerous for the fish.

Furthermore, ensure that you are feeding your fish only as much as they need to eat (overfeeding is very common to new aquarium owners). You should remember that any food that is not consumed by your fish will eventually be decomposed and increase your ammonia levels of your tank (this will further strain your filter which is already struggling trying to cycle). You can help your filter cope with the increase in ammonia levels by getting a gravel cleaner (another important tool for your tank).

Finally, to ensure that your aquarium is properly cycled:

  • Dechlorinate your water and ensure that all water that enters your tank from now on is dechlorinated
  • Get a test kit and start monitoring your ammonia and nitrite levels
  • Perform 25% water changes every other day (until you get a test kit I would advise doing 25% daily to ensure that the ammonia levels do not increase in dangerous levels). Your water change should ideally be done through gravel cleaning
  • Ensure that you are not overfeeding, if you see that your ammonia/nitrite levels are high, do not feed your fish for a day (most fish are fine without food for 2-4 days)
  • Wait until your test kit reading shows zero ammonia and zero nitrites for at least a week
  • Most importantly of all, DO NOT introduce any more fish in your aquarium until your tank has cycled
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  • Thanks @VasilisC for your ideas. I forgot to mention this but I have been using de-chlorinated water in my tank from the very beginning. Also, I'm feeding them only small amounts of food which they eat almost instantly. And I'm concerned with cleaning the gravel because that might disturb the good bacteria which is there in the gravel bed. Also, If I do 25% water changes in that small volume of water, will that not stress the fishes? – 0x550x42 Jan 4 '16 at 10:36
  • @0x550x42 - Although the gravel does contain some beneficial bacteria, the bulk of it lives in the filter itself. If you do perform daily water changes (when your bacteria colony is small to non-existent at the beginning of the cycle) then I suppose you wouldn't need to gravel clean every single time but only when you see that there's a good increase in fish poop (there shouldn't be many food leftovers, if any at all, since you are careful with how much you feed your fish). About stressing the fish, to be honest this is the lesser of two evils as it is preferrable to ammonia/nitrite poisoning. – VasilisC Jan 4 '16 at 11:02
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You have two fairly large fish in a relatively small aquarium which is going to create a fair amount of ammonia. To speed cycling and minimize ammonia effects on your fish, I'd get some de-nitrifying bacteria in the tank ASAP and do larger water changes. If you have a friend with fish, you could take some squeezings of their filter media and add it to yours or you can buy such bacteria commercially. In the meantime, a daily 33-50% water change is going to be much more helpful in knocking down ammonia levels than the smaller amounts you mentioned. Finally, I highly recommend live plants where possible as they soak up ammonia for their own use. I have a couple goldfish in a 5 1/2 gallon tank, no filtration, but a bunch of water lettuce and my ammonia levels are 0 ppm and my nitrates are only about 5 ppm.

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  • thanks a lot for sharing your experience. I also feel that i need to do daily water changes but when i told the person at the fish store about this, he told me that daily water changes would be stressful for the fishes.. I am still confused... – 0x550x42 Jan 3 '16 at 18:58

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