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Small Tanks Don't Cycle? What??

974 Views 7 Replies 5 Participants Last post by  cl3537
Hello all,

I'm new to the aquarium community and am trying to get some reliable information regarding cycling.

I currently have a 5 gallon planted tank (fluval spec V) which is generally doing well. It has been running for a few weeks. Unfortunately, I didn't have the opportunity to cycle this tank at all. The tank ran for about three days with plants only (and prime treated water) and then a betta was added. I do not see any signs of stress and the fish generally seems happy.

My understanding was that the tank must be cycled before fish are added. I am aware of fish-in cycles as well. Recently, I've been reading that tanks under 10 gallons do not cycle, or do not require cycling. I've read that water changes never allow the bacteria to grow effectively when the tanks are this small, leading to unstable conditions. Is this the case?

With the rise of the nano and desktop tank, I find some of this information hard to believe. Will my tank crash? Should I be doing more water changes? Do smaller tanks require more water changes/cleaning/maintenance than larger ones?

Also, I am awaiting a liquid test kit, but my parameters (using test strips) are reading 0.5ppm nitrite and 40ppm nitrate, with moderately hard water and a neutral pH. I'm trying to figure out what I am supposed to be looking for in these parameters. I realize that the nitrites should be 0 and am doing regular 50% water changes.


P.S if anyone has a similar 5-10g planted setup, what is your maintenance schedule?
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Wow! These are all very thorough responses. Thanks for sharing your knowledge! I think I can see why there are misconceptions about tank cycling as well. Thankfully these responses helped clear these up!
While I did a fishless cycle with minimal plants by adding small controlled doses of ammonia, few have the patience to do this.

Bettas are very hardy fish if you had any ammonia it wouldn't bother them as much as other fish, look how the fish stores keep them in little cups. If you are feeding sparingly 1 betta with heavy planting the plants should consume the ammonia. That doesn't mean the tank isn't developing BB and doesn't mean the cycle isn't completing.

If you plan to add more sensitive fish, wait a few more weeks and do so slowly. Getting an API Ammonia kit and testing will help, don't do a water change for 2 - 3 days and then check your Ammonia, if you don't have any or 0.25(test is poor at distinguishing between 0.25 and 0) you are fine. Classicly if the cycle is completed you should have 0 Ammonia 0 Nitrites and be building up nitrates slowly. However given you have plants and a low bioload you may never see the nitrates build up.
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