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New Fishkeepers Blog - On yer bike! (Tank Cycling)
Category: Tropical

Author: Ants (7:15 pm)
Saturday, the water has cleared up nicely and my ammonia plus syringes have arrived. Yay, I can start cycling my tank. I'm following the excellent guide here: ... hless-cycling-article.htm

I chose the ammonia version as the "fish food" method seems too risky, how much food and when to add it seem like an accident waiting to happen and I've read a couple of forum posts involving this method which don't look like they have been particularly successful!

A test of my water parameters gives me Ammonia (NH4), Nitrite (NO2), and Nitrate (NO3) readings of ZERO with a PH of around 7.4.

To cycle the tank I should be aiming to have 3ppm of ammonia in my tank at the start of each day, this should get converted to nitrites and finally to nitrates by the filter bacteria. Once the tank is capable of converting 3ppm of ammonia into nitrate each day the tank is cycled and ready for fish. (The tank readings should be zero ammonia and zero nitrites 24hrs after adding 3ppm ammonia to the system)

Using the handy calculator at the bottom of the guide I calculate that to add 3ppm ammonia to my tank I have to add 1.5ml, this works out as 0.5ml is roughly 1pmm a nice easy calculation.

|_Day_|_Ammonia_______________|_Nitrite_|_Nitrate_| Notes
|__1__|_0 -> add 1.5ml (3ppm) ______|___0___|___0___| Add Carbon to filter
|__2__|_2 -> add 0.5ml (1ppm) ______|___0___|___0___| Added air pump/air stone
|__3__|_2 -> add 0.5ml (1ppm) ______|___0___|___0___|
|__4__|_2 -> add 0.5ml (1ppm) ______|___1___|___5___| Nitrites and Nitrates first appear in tank
|__5__|_1 -> add 1.0ml (2ppm) ______|___2___|___5___| Replanted a plant disloged by airline.
|__6__|_0.25 -> add 1.3ml (1.75ppm)__|___5___|__10___| Snails start appearing in the tank
|__7__|_0 -> add 1.5ml (3ppm)______|___5___|__20___| ammonia -> nitrite cycle is established?
|__8__|_0 -> add 1.5ml (3ppm)______|___5___|__20___| 15Liter (approx 30%) water change
|__9__|_0 -> add 1.5ml (3ppm)______|___5___| no test |
|_10__|_0 -> add 1.5ml (3ppm)______|___2___|__20___| 10Liter (20%) water change
|_11__|_0 -> add 1.5ml (3ppm)______|___0___|__10___|
|_12__|_0 -> add 1.5ml (3ppm)______|___0___|__20___| Nitrite -> Nitratre cycle established?
|_13__|_0 -> add 1.5ml (3ppm)______|___0___|__20___| 10Liter (20%) water change
|_14__|_0 -> add 1.5ml (3ppm)______|___0___|__40___|
|_15__|_0 -> add 1.5ml (3ppm)______|___0___|__40___| approx 70% water change
|_16__|_0 -> STOP ADDING!_______|___0___|___5___| FISH IN!

So it took me 2 weeks to cycle the tank, looks like some of the old filter bacteria survived. From a standing start this process should/could take 4 to 6 weeks. If you know someone who keeps fish you may be able to get some used filter media and tank water from them to achieve the same result.

A bag of carbon was added to the filter because the wood was turning the water brown. This is a natural process as the wood leaches tannins into the water which can last for months and I didn't fancy boiling the wood for several hours as some people suggest! Whilst not harmful to the fish (some species may even find it beneficial) it can look unsightly, the carbon will remove some of this (and other unwanted toxins) from the water. That's now almost due to be removed as it apparently loses it's effectiveness after 5-6 weeks and can even start leaching any toxins it's collected back into the water.

The air pump/air stone were added because I was getting a film over the surface of the tank, which could indicate inadequate surface movement and low oxygen exchange. I later changed the pump which had become noisy and fitted a spray bar which also increases surface agitation. In a planted tank the plants will produce oxygen, BUT this only happens whilst the lights are on, in the dark the plants will also use oxygen (and give out carbon dioxide) so an air pump may be required to stop O2 levels dropping too low in the night. This is on 24/7 at the moment, but I'm wondering if it might be better to add a timer and only have this on when the lights are off? (comments are welcome below)

Part way through the process I started noticing "brown dust" appearing on some of the plants. At first I thought this might be something falling into the tank, but an online search revealed that this was brown diatoms (a type of algae) which are absorbing silicates in the tank (from the substrate etc.). This is apparently quite common in newly cycled tanks, and should eventually settle by itself. It can be "wafted off" plants by moving the water around them or removed by vacuuming them when doing water changes.

Once the tank is cycled it is important to keep topping up the ammonia until fish are added to keep the cycle going. You should add the last ammonia 12 to 24 hours before putting fish in, and check ammonia and nitrites are both ZERO with low nitates before going to the local fish shop.

The series of water changes in the final few days was done to remove/dilute the nitrates in the tank, ultimately I had to do a big (approx. 70%) change to get it down to a low starting level. This will hopefully be maintained with smaller weekly changes of around 20% once fish are in the tank.

I hope someone is finding this blog interesting (or helpful). Comments are welcome below.

Next time: The plants.
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  • Home away from home

 Keep it coming

I'm enjoying your blog :D

  • Just popping in

 Re: Keep it coming

Thanks, nice to know. I'll try and get some more up next week.

  • Just popping in

 Helpful Info! Question about Fish Insurance.


I just came across your blog and I really enjoy reading it. I have somewhat of an off-topic question for you-- do you know anyone who does fish insurance in the UK?

Thank you!

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