I have a theory

This is an observation I have made from personal experiences and from experiences of many others around me. Please feel free to argue this.

When you start up a new tank, there is more that goes on than just the biological cycle in the first few weeks... lets look at it from a few angles: microbiological, macrobiological, and chemical. First consider the constants of every tank; new undeveloped sand, uncultured live rock, new plastic pumps/powerheads, brand new saltwater, and a "clean" system.

Chemical- you are adding a lot of unnatural things to your tank. The sand is not thriving yet, the rocks may have bacteria, but not near enough to hold any chemicals stable. The nutrients of the system are through the roof at this time! Silicates are leeched into the water from virtually everything. And any other mystery chemicals that may have hitched a ride in somehow... Now over time all these negative chemical influences will be taken care of one way or another by establishing stability in the tank. Your biological filter will "learn" how to process the high nutrient levels and the nasty chemicals over time.

Microbiological- You start out with a few bacteria, they rapidly multiply... but think about it, the species that is most efficient at nutrient uptake will take over the tank first, this may be fast, but obviously not be the most efficient bacteria! The most efficient bacteria is the one that can break down a vast range of organic (and possibly inorganic) molecules. They typically grow slower but are much more effective for the tank. Once the really fast guys use up all their energy source, they start to die off and the stronger/better/slower reproducing bacteria will slowly take over (until the next stronger/better/slower reproducing bacteria comes along). Over time this happens naturally and this is why the older tanks are always more stable.

Macrobiological- There are no trophic levels for degradation of complex molecules yet... a hierarchy must be established. With a new tank there just arent many organisms to efficiently fill the various gaps in the trophic food chain to make the processing of waste efficient. Your basic food chain at birth of tank: fish --> snails --> bristleworms --> bacteria. An established tank may be like this: fish --> shrimp/starfish --> snails --> various worms --> copepods/ other small fauna --> plankton --> clams --> algae --> corals/zooxanthellae --> bacteria. You cant introduce something at the top of the chain and expect the bottom of the chain to instantly be able to compensate for the nutrient increase! As you can see though, the nutrient export process has many more levels in aged tanks and each specific niche can be filled by its own representative organism given some time.

In summation, there is more to a "cycle" than just ridding the tank of ammonia, nitrite, and nitrate... it is allowing your tank to establish its own highly efficient, sustainable ecosystem.

 

I agree

 

IME, A tank is not fully cycled until at least a yr like mission stated. "Ceteris Parabus"
What is your take on larger systems say like 5000 and above sea quariums.
Do these "cycles" take the regular average 8week cycle or much, much longer?

 

Completely agree..I just started noticing that my tank was actually stable about about 2 or 3 months ago after starting it over a year ago.

 

It would be interesting to see... But I would assume they would take linger because they have a much larger food chain in them and some links can easily be missing...

 

Check this out

 

I agree 100%. Part of the reason why I only have 2 gobies in my new system and it's been setup since late October, I just added coral to it 2 weeks ago but mostly because I was forced to by circumstances from my old tank.
I'm just now starting to see little worms and lots of little worms/shrimp/pods running around.

 

Wow!!! That's exactly what I'm saying!

 

Yep, I'm with you Dingo. When i set up my tank I read a bit about the various bacteria and microfauna that do the "dirty work" in my tank.

I think the Secret Cycle article is accurate, but conservative.

When I started my tank I first read about people letting their tanks cycle for 6+ months before intentionally adding ANY livestock other than live rock. That idea alone nearly turned me off from the hobby.

Then I saw the other route that many people often take, which is set up day one with fish any artificial plants/rocks/corals and the massive die off that occurs, and thought how cruel that was.


Then I found 3reef and talked to people at the LFS and found a happy middle ground. I set up my tank with mostly live rock and live sand, never saw any major rise in nutrients, and after less than 2 weeks the nitrogen cycle seemed complete. I added 3 blue green chromis. All was fine. Still is.

Yes, I had diatoms, cyano, algae, etc, but nothing that hurt the fish.

At 10 months out now I know I still have things going on in my tank that I cannot see.

But I also operate under the knowledge that cycles and changing of the guard so to speak will NEVER stop in a healthy marine system. Every time a fish poops, temperature changes a degree, of the lights turn off the ratios of bacteria will change. Some bacteria have generational lifespans measured in seconds, others decades.

Point is, while I agree that it can years for a tank to become "mature", stability is a relatively subjective term. Cycles never end. At some point you have to decide when to add fish and other live stock, and from my research the opinion on that is when the nitrogen cycle has leveled off to very low numbers.

While further prudence may be required when housing very rare or delicate species of fish most of us seem to start off with mostly damsels of various makes and models.