The Planted Tank Forum banner
1 - 3 of 3 Posts

· Registered
10 Posts
Discussion Starter · #1 ·
Hello all,

I have had a bit of a break from keeping fish and recently set up a 15g Fluval Flex planted aquarium. I set the tank up and added the live plants on 15th Jan and have been testing and today, I am measuring nitrates, it seems too early in the cycle but I'm wondering if this could be down to it being planted? (I've had reef tanks in the past so this is all a bit new to me)

Please could you let me know if you think I'm doing okay with regards to the tanks cycling process?

The tank is set to 24 degrees and it's a fishless cycle, I'm dosing with Dr Tim's Ammonium Chloride, this is my results so far.

16/1/19 - Ammonia = 0.25 or less, Nitrite = 0, Nitrates = 100, PH = 6.8-7.2 via test strips - I then added Ammonia after test (50 drops)
17/1/19 - Ammonia = Between 1.0 and 2.0ppm, after test, I added 5 litres of water to top tank up
18/1/19 - Ammonia = Between 0.50 and 1.0, Nitrates = 0, Nitrates = 25, PH = 6.4 via test strips
Test after adding 60 drops Ammonia, aiming for 3ppm of ammonia
18/01/19 - Ammonia = 4.0
21/1/19 - Ammonia = between 2.0 and 3.0, Nitrite = between 2 and 5ppm, Nitrates = 40-80ppm, PH = 7 via API Test

The first few tests I used the dip stick tests (apart from ammonia so I'm not 100% sure how accurate those readings were) but today I used API so I'm on day 6 of cycling with Ammonia = between 2.0 and 3.0, Nitrite = between 2 and 5ppm, Nitrates = 40-80ppm, PH = 7 via API Test

I'd really appreciate any advice, and should I keep dosing with ammonia to try and keep around the 3 ppm mark?

Thank you very much!


· Banned
306 Posts
The presence of nitrites suggests the tank has begun to cycle, but the cycle is not complete.

If you are trying to build up a robust biological filter, in preparation for adding fish, then yes. You want to continue dosing ammonium until the fish are about ready to go in the tank. During the early stages of cycling, maintaining 2-3 ppm ammonium is probably a good approach. Eventually, though, the filter will build to the point where it's hard to maintain the concentration of ammonium because it's converted to nitrate so fast. This is a good thing, of course, because there should be no detectable traces of either ammonium or nitrite in the water when the fish go in.

So how do you know how much ammonium to add? In principle, once you've cycled, you add ammonium at the same rate your anticipated stock of fish will be putting it in the water. When this almost immediately disappears, and no nitrite is detected, the tank is ready to go. Unfortunately, I've never found handy tables for ammonium production by fish. But if you can estimate how much food the fish eat each day, you can then estimate the amount of ammonium they produce: Fish food is typically about 45% to 50% protein (except for vegetarian foods like algae wafers; they're more like 30%-35%). Let's go with 50%. On average, protein contains about 16% nitrogen. This means a gram of fish food contains about 80 milligrams of nitrogen. That's equivalent to about 300 milligrams of ammonium chloride.

I doubt I feed my fish in my 55-gallon display tank more than a couple of grams of food a day. (For rough estimating, a gram weighs about as much as a U.S. dime coin or a single strand of spaghetti.) So if I was cycling my tank to hold about that number of fish (six rainbows, four SAE, two rams, nine otos, an ancistrus, and a grouchy old clown loach), once the ammonium started to drop, I'd start working up to about 600 milligrams of ammonium chloride a day added to the tank. That's very roughly an eighth of a teaspoon. In my 55-gallon tank, that would be about 3 ppm when it first goes it, but it disappears very quickly if the cycle is up.

So it really doesn't take much ammonium chloride to keep a filter alive. And there's little harm in being generous with the ammonium chloride, other than needing to change the water more frequently to keep nitrate at a reasonable level. Your tank is much smaller than my 55 gallon, but you have live plants competing for the ammonium, so you could try 1/16 teaspoon a day as your target.

So the scheme is: Keep the ammonium level at around 2-3 ppm until you're having to add about a sixteenth of a teaspoon a day to keep the level up. Then continue adding a sixteenth of a teaspoon a day until ammonium and nitrite are undetectable within a few hours of adding the ammonium chloride. At that point, you're fully cycled and ready for fish.

· Registered
10 Posts
Discussion Starter · #3 ·
Thank you so much for your detailed reply, that is a huge help and very reassuring, I really appreciate you taking the time to go into detail for me :)

I am sorry for the slow reply to you, I did reply before but I must not have hit submit, I have a baby and I suspect I got distracted halfway through!

I am planning on adding a small shoal of something like 7 harlequin rasboras or ember tetras, do you think once the tank has completed it's cycle I could add the 7 in one go, or would I be better adding say 4 and then another 3 in a couple of weeks once the tank has cycled again with the new load?

Thank you :)
1 - 3 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.