Loaches and "mature" tanks

[san-ho-zay]

OK, planning ahead a little here. My tank is fishlessly cycled and partly stocked with danios and barbs. I've seen recommendations that loaches should only be added to a mature tank.

What's the rationale behind that and what's a mature tank? 3 months, 6 months, a year? What do loaches get in a n-month old tank that they don't get in a relatively new, but stable tank?

How much of the 3-6 month recommendation is based on the "old" method of cycling with fish?

And how does that work with a quarantine tank? What constitutes a mature quarantine tank?

And no, I'm not about to rush out and buy a group of loaches.

[Diana]

Many sorts of bacteria and fungi live in a mature tank. There are not great swings in the population. Conditions are stable.

These microorganisms live in what is called a biofilm. This is a layer that feels slimy to us, but is actually a complex structure with channels for the water to flow through, and many sorts of things living side by side.

When you are cycling a tank you are specifically interested in growing the nitrifying bacteria, but all these others come along, too. They decompose waste, eat each other, lock up heavy metals and all sorts of activity that might seem chaotic, but actually meshes together quite well. What one creates as waste, another eats as food.

Net result is a matured tank with an ongoing ecosystem.

As for how long this takes... I dunno. More than a couple of weeks, I am sure. Couple of months? Probably. A year? That is a long time.
If you can keep the conditions stable in a new aquarium I think the biofilm will develop quite fast. If you have changing conditions, need to medicate the fish, change your mind and throw out all the gravel... the 'mature tank' is going to be delayed.

I sometimes wonder if the statement "Do not add this fish to a new set up" REALLY means "Do not start learning about aquariums by adding this fish to your first tank"

At this point in time all my aquariums are well established. If I change anything I am usually keeping most of whatever it was, or taking something from a different (established) tank, so that while I am disturbing some of the biofilm overall the tank is still (IMO) a mature tank.

Even my quarentine tank has been set up and running for a long time. I keep fish in it, but move them a day before I get new fish.
When I get new fish I will alter the water in the Q-tank to match the water in the bag (pH, KH, GH, TDS) then drip the fish in a bucket for an hour or more, then add the fish to the Q-tank.
There is one local store where the water is very hard, and the owner runs salt in everything. At another store they run several systems and I need to check each time for which system the fish came out of. This sort of thing (Different water at different stores and my changing the q-tank water to match) might cause some of the organisms in the biofilm to die. The algae and plants do not seem to mind, though the salt sets them back a bit.

Perhaps another part of 'Mature tank' is really an aquarium keeper who knows how to treat the water at water change time, and keep on top of conditions so the tank stays stable; the water parameters cycle around some fixed point, never getting too far out of hand.

[san-ho-zay]

Diana,

Thank you. You always post very eloquent responses packed with information and wisdom .