Fishless cycling filter on a smaller container


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Aug 20, 2017
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Hi first post here

I was trying the fishless cycling using ammonia ( using the "Add and Wait" Method but instead of using my 70gal aquarium I used a 20gal container that fits two 4 in diameter x 4 in height sponge filter. Actual water is only 10gal, just half inch above the filter.

My plan was cycling the filter to produce bacteria on a small container. When my cycle is complete I will transfer my filters and 7gal of the cycled water to the 70 gal aquarium. The aquarium water will be aired for 2 days passing thru an active carbon connected to my faucet before mixing the cycled water and filters. This way I only throw a few gallons of water.

I'm currently on my 9th day and my ammonia is not dropping. I set it at 3ppm. The bottle says "Strong Ammonia" bought at a drugstore. I did the shake test and no bubbles formed. But under its uses its for cleaning, so not sure if this kills bacteria instead of feeding it. When I opened the bottle it had a very strong smell like someone punched my nose. I'm using API Freshwater Master Test Kit. But instead of using 5ml water I used a syringe to get a ratio of water needed for 1 drop of the test kit, i.e. 0.625 ml for 1 drop of Ammonia test, 1ml for 1 drop of Nitrite test,...

Here is my record: pH 7.6, Ammonia ~3ppm, Nitrite 0, Nitrate 0, Temp: 83 deg F (I use a meat thermometer, is this accurate for water measurements?) No change since day 1. I test every other day.

Am I doing something wrong with my setup?
Do you have the means to test your Gh and KH? I read some where that low levels an have an affect on cycling this way.
First of all, I would stop using that method of cycling as it is now out of date, and instead follow this one
Since you have only added 1 dose of ammonia just carry on from day 2 in the newer method.
The add and wait method makes so much nitrite that it stalls the cycle. The newer method is designed so that the nitrite level can never cross the stall threshold. And we now know that the bacteria won't die if ammonia is not added every day.

It took 4 weeks for my ammonia to drop to zero when I did a fishless cycle. 9 days is a lot less than that, you need to be patient. And I used ammonia meant for cleaning, the bottle didn't say so I emailed the company to check there was nothing else in it.

I would use the test kits as per the instructions, ie use 5 ml water. The bottles will last long enough to do a cycle particularly as you don't need to test every day at this stage.

Nic1's point about about GH and KH is because it is harder to cycle in soft, acidic water. And with low KH, the pH is likely to drop so low that it inhibits the cycle. I know, I have KH 3. At this stage, just look at your water supplier's website for the hardness and, if they give it, alkalinity (which is water water companies call KH). You need the number and the unit as they could use one of about half a dozen different units. Post them here and we can see if they are on the low side for cycling.

Using a smaller container to cycle the filter in is fine as long as you add no more than 3 ppm doses of ammonia. But you will need to remember that ppm is not an absolute measure like ounces or grammes. It is a proportional measure, so the amount of ammonia that gives 3 ppm in 10 galls will give a reading of 1 ppm in 30 galls and 0.43 ppm in 70 galls. When your filters are cycled to 3 ppm in your 10 galls of bucket water you will have grown 1/7 of the number of bacteria you need. You will need to move them into the tank and continue by adding 3 ppm ammonia and following the cycle method again until the tank can cycle 3 ppm ammonia in 70 galls. This won't take nearly as long as in the bucket because we start off with only a very tiny amount of bacteria and getting them started is the longest bit. Once you have a seventh of the amount you need it will take only a few days to grow more.
Personally, I would fill the tank and put the filters in there to cycle them. It won't take any longer. And you won't waste any water as you don't need to do a water change during fishless cycling - unless you use the add and wait method resulting in so much nitrite you have to do a water change to lower nitrite.

Can I ask why you need to run the water through carbon?
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Thank you for your replies.

I just read the new fishless cycle.

I do not have a GH nor a KH tester. I'll try to get one.

Our faucet water has chlorine so I put an active carbon to eliminate or at least reduce it.

BTW, I initially made a mistake that I poured the whole bottle (60ml) of ammonia on a 20 gal container following on a friend's advise which turned my ammonia test bluish. After a month of no improvement I realize that he has a pond not a 20 gal container. I searched the internet and found the article I mentioned above. I took another container placed 10 gal of water and poured about a cup of water (I did not really measure it since it was a trial and error until I had 3ppm) from my first container as describe on my first post.

NOTE I just assumed I have a 3ppm ammonia since the color is somewhere between 2 and 4 ppm. It could be nearer to 4 ppm.

Did my initial mistake has any effect on my fishless cycle? I did not clean the filters when I did my 2nd attempt.

Is the sponge filters enough? The only air source I have is from the sponge filters? Do I need to have an air stone?

...And you won't waste any water as you don't need to do a water change during fishless cycling...

essjay, I do not understand what you mean by this. In the new fishless cycle article advice to do a large water change when ammonia and nitrite is 0ppm

Next weekend I will setup my aquarium and continue my cycle.
The majority of tap water has chlorine or chloramine in it. Only well water doesn't. So we add a dechlorinator to the water to remove the chlorine. Tap water also has metals in it it and these dechlorintors usually have a second ingredient which binds these metals. Most of them also have a third ingredient which detoxifies ammonia for 24 to 48 hours. This is because a lot of water companies use chloramine rather than chlorine. This is an ammonia and a chlorine joined together. The first ingredient splits them up and the ammonia detoxifier makes it safe until the bacteria have had chance to 'eat' this ammonia. And a lot of them also contain something to 'stimulate the slime coat' which is not needed.
I use API Tap Water Conditioner as this one contains only the first two ingredients (I have chlorine not chloramine so I don't need an ammonia detoxifier)and is very concentrated.
Do you know if you have chlorine or chloramine in your tap water? Chlorine will gas off on standing but chloramine won't. You have to use a dechlorinator to remove this. And letting the water stand won't remove any metals in there.

Yes, you do have to do a water change at the end of the cycle which is to remove all the nitrate made during the cycle. But with the add and wait method it is common for the cycle to stall and then a water change has to be done during the cycle to remove the nitrite which has stalled it.

And of course once you have fish you will also do a weekly water change of around 50% of the tank volume. Unless you have somewhere to store 35 gallons for a couple of days (assuming you have chlorine not chloramine) you will need a dechlorinator to treat the new water gong in the tank. Would your carbon filter be up to treating 35 gals of water every week in the short time needed for a water change?

As long as the ammonia is now between the 2 and 4 colour, that's fine. But I would still use 5 ml water and the number of drops on the bottles. That way you can be totally sure it is 3 ppm-ish. When you added that overdose at the beginning, it would have been so concentrated that the bacteria we want wouldn't grow. As long as you don't add more than 3 ppm again, it should be fine.

To be honest I don't know if 2 sponge filters will be enough for 70 galls. I have one in my betta's tank but that's only 7 galls. I have 2 internal filters in my bigger 47 gall tank. My worry would be that they wouldn't be able to circulate the water properly, but hopefully someone who uses sponge filters on large tanks will be able to advise you better than me.
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3 ppm is just the amount chosen for fishless cycling when the filter is in the tank it will be used in. 3 ppm is more than a properly stocked tank of fish will make in 24 hours, so using this amount ensures that there are enough bacteria at the end of the cycle. You can use a high ppm up to a point, but that means you grow a lot more bacteria than will be needed.
Cycling in a container than is smaller than the tank the filter will be used in means it will grow less bacteria if 3 ppm is used, but at something like 8ppm the bacteria we want stop growing and another species grows instead.
And there is a problem further down the line. If more than 3 ppm ammonia is used, the ammonia eating bacteria will make a lot of nitrite - and high nitrite is known to stall the cycle.

But in your case, you are not cycling the filter, you are keeping alive the bacteria that are already in a cycled filter. I would stick to 3 ppm every 2 or 3 days, then once the tank is ready, move the filter into there and add 3ppm to check there are still enough bacteria.
If you have enough well growing live plants in the tank, they should take up a lot of ammonia, if not all of it, so you may not need to test the filter once it is in the tank. And adding 3 ppm ammonia may not do the plants much good. Fish make ammonia constantly all day long, a bit at a time, which is not the same as us adding a day's worth of ammonia in one go.

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