Cycling a 20 gallon high aquarium

[Silverfish97]

Hello, I am new to this forum and a novice in fishkeeping (I have some experience but not a lot; mostly with bettas). My new 20 gallon tank is currently in the process of developing its biological filtration cycle. I'm doing a fishless cycle with flakes. The tank was set up on Tuesday (5 days ago). I added a few pinches of flakes immediately, used 2 heaters to bring the water to 86 degrees, added an airstone, and put in some Stress Zyme.
Over the past few days, I've tested the water's ammonia, nitrites, nitrates, and pH each morning. The ammonia has barely gotten to 1ppm. The nitrites have stayed at 0 or between 0 and .25ppm; the color in the test tube is a little confusing. Each day, I've added another pinch of flakes to the water (it's caused a rather unpleasant smell; I don't know if that's normal or a sign of too many flakes).
Yesterday, I seeded the tank with bacteria from a mature 5 gallon tank by putting some of its gravel in a clean filter cartridge mesh bag and placing it in the 20 gallon's filter with its cartridge, and added some more Stress Zyme. The readings this morning indicated decreased ammonia (about .25 ppm), zero nitrites, and an increase in nitrates (it was 0 yesterday and now reads about 5ppm). The pH has been a steady 7.6. The hardness I don't know, but my area is considered to have hard water.
I've read that decreased ammonia and nitrites, coupled with an increase in nitrates, indicates a completed cycle. I seriously doubt that the tank has cycled itself so fast. What, then, is happening in the tank? Does anyone have some advice? I don't want to rush the cycle and add fish to an unprepared tank. An experienced fishkeeper's advice would be greatly appreciated.
Whatever's going on in there, I'm going to wait for at least a week or two and keep watching the chemicals' readings to see if they stabilize before I even think about buying fish.

 

[FreshyFresh]

I can pretty much assure you that nothing is going to happen in 5 days with a fishless cycle by adding fish food. First the food has to rot to the point of nastiness, where it forms ammonia. This alone will take a week or more. Waiting for the nitrite spike is another few weeks. I've not seen a fishless cycle happen in quicker than a month.

You are on the right track by using some used substrate out of a mature tank, but a better method is to use some of the biological filtration out of the mature tank. This will basically be an instant cycle for you and you can stock lightly, immediately. Still have to test your water parameters and be ready for a emergency water change though.

 

[Silverfish97]

Thanks for the swift reply. By "use some of the biological filtration out of the mature tank", do you mean a used filter cartridge? I could take the filter cartridge from the 5 gallon and put it into the 20 gallon's filter, and put a fresh cartridge in the 5 gallon's filter, but would that destroy the 5 gallon's biological cycle and endanger the betta in that tank?

 

[FreshyFresh]

I wouldn't remove all the filter media from the 5, but could you use some of it? Most use a throw away floss cartridge and then a foam pad as the bio media. Others use a reusable sponge and then a separate bag of bio media.

This is why a lot of us run more than one filter on a tank, so you can swap one of them over to a new tank should you need to.

 

[Silverfish97]

The filter is quite small. There's no room in it for any more than its cartridge, which is a floss bag with charcoal. The rest of the filter's parts are non-removable. The tank's lid doesn't have an opening to fit a second filter. I can't take only a portion of the media; I would have to remove and replace the entire cartridge.

 

[Silverfish97]

I removed the 5 gallon's cartridge (which was I don't know how many months old and very nasty looking, almost ready to fall apart) and placed it in the 20 gallon's filter. The cartridge and the bag of gravel wouldn't both fit in the filter, so I put the gravel back in the 5 gallon. The 5 gallon's filter now has a new cartridge. I'll keep a close eye on the readings for that tank for a while to make sure it stays all right for my betta.

 

[FreshyFresh]

With the established filter media installed in the 20H, you'll need to either keep providing it with an ammonia source, or better yet, just stock it (lightly) and keep an eye on your water parameters.

 

[Silverfish97]

I'll continue letting the flakes decompose for now.

 

[FreshyFresh]

That's fine, but based on what you said above, if the ammonia is being processed into nitrate, you should be ready to lightly stock.

If your water supply uses chloramine as opposed to chlorine for a disinfectant, you will see trace ammonia after it's added to your tank, so the 0.25ppm you see, could be from that.

 

[Silverfish97]

The ammonia and nitrites have reached 0ppm and the nitrates are between 0 and 5 ppm (I'd guess it's about 3). The pH is still 7.6. Will begin thinking about lightly stocking. I'd like to keep Harlequin Rasboras, but I've heard that they are on the delicate side. Would corydoras be a suitable first fish?