What separates an immature tank from a mature tank?

[apr28]

I was thinking about how people recommend certain fish for well established tanks like certain types or rams or clown killifish.

But what constitutes an established tank? If a young tank is cycled and water parameters hold steady for weeks, wouldn't that tank be considered established and ready for anything? (Assuming PH levels and temp are where they're supposed to be for a specific fish)

I am definitely not questioning the logic where I think it's ok just to throw any fish in a tank. I enjoy the hobby and as my learning and confidence grow I may be willing to take chances with more difficult fish.

 

[Luananeko]

In certain cases, an "established" tank has had time for microfauna and microfilms to grow because this serves as food for said fish that needs an "established" tank. For example, you would never want to add an Oto to a tank that has only been running with stable parameters for a month because they would quickly exhaust a food supply that cannot easily be supplemented. In cases like this, I tend to err on the side of caution and suggest a minimum of 6 months of stable parameters before adding these fish.

As an example of a different style case, Rams do not rely on a tank being established for their food supply, so you have more lenience there. They just need the tank parameters to not go out of whack. In this case, you can add them once you've added the bulk of your other inhabitants and observed stable parameters for a few weeks to a month. The main concern I'd have with adding them earlier would be that the early stocking phases tend to have more parameter swings from a frequently changing bioload. Also, Rams are territorial, so adding them early means new tank mates would be treated as intruders rather than existing inhabitants. Delaying adding them allows the existing inhabitants and water parameters to settle before adding more difficult (both in personality and needs) fish.

 

[Old Scales]

I can't say there is an exact biological analysis of why an established tank is better for sensitive fish than a newer tank. If there is info on it out there, I haven't found it yet. It may have to do with an older tank has built up various biofilms and micro organisms that fish have evolved with that helps them metabolize better. Just like we have to have beneficial bacteria in our guts to live, it may be the same for fish. Our treated water and new tank surfaces don't have any of that. Most people think of a new tank as one less than four months old.
It's been experienced over many years that sensitive fish fare better in the older tanks. If anyone out there knows the exact biology of this, I would LOVE to know. Even with that, the knowledge we now know of fish keeping is light years ahead of what we knew 20 years ago. When I got into this hobby 50 years ago we were REALLY in the dark ages compared to now. OS.

 

[Fishfur]

I'm afraid I don't know the precise biology of this either but I have always assumed, dangerous though that may be, that it is the build up of biofilm and heterotrophic bacteria in older tanks that makes the difference. New tanks have very little biofilm, and shrimp and Otos, among others, feed on this heavily. So there has to be a decent layer of it on most, if not all, of the surfaces, to support them.

Plants seem to play a role too. Planted tanks seem to mature faster, at least, those I've had that are planted appear to have more biofilm sooner than tanks lacking plants. Using rocks or wood from an established tank seems to help some too.. perhaps not unlike seeding a filter.

Shrimp, Oto cats and many loaches are just a few of the species said to do best in mature tanks. I have found, through my efforts at raising Ghost shrimp, that adding green water to a tank helps establish biofilm much faster than it otherwise would build up. Not at all sure why that happens but it does happen. This is along the line of adding about 100 CC of cultured green water to a 5G tank twice a day for a few weeks, while the shrimp are larvae and for awhile after they morph.. about 3 weeks altogether.

By the end of the 3 weeks, the tank was supporting baby shrimp without my having to feed them anything at all, though of course I did feed them.. but only once a week. A few microworms, a fragment of algae pellet or tab, once a week or so.

For now, that's all I know, but experience with my tanks over the past couple of years seems to support the biofilm as being at least a large part of this.. if not the whole of it.

I think 4 months would be the minimum, and 6 months is better, if you aren't adding green water or used rocks or plants to a tank.