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I have another question...

If i put water from my L134 aquarium into another aquarium... and give it a filter from the L134 aquarium...
Is that aquarium save for my fish?

There is nothing "magical" about old aquarium water - the only reason to transfer water from one tank to another is that it's the same as the tank it came from - so for fry and other fish that you move from one tank to another.

The "magical" bit in an aquarium is the filter media in a mature filter. That's really the only thing that make a big difference when setting up a new tank.

And yes, if you move a mature filter from one tank to another, that makes the tank ready to take some fish - how much fish it can take depends on the size and load the filter has been coping with - if you have 5 medium sized fish in a tank and move the filter from that tank, then you can't expect the filter to take on 20 medium sized fish (or 5 XL size fish). If you have three filters, of the same size, with 15 medium fish, it's fair to expect it to cope with 5 medium sized fish. It gets extremely complicated when the filters are different sizes, and I'm not going to even try to explain how you'd calculate that exactly - suffice to say, if you have two large and one small filter in a tank with 15 medium sized fish, the small filter is most likely not going to cope with 5 medium sized fish, because the amount of biological filtration going on in each filter is not equal.

Finally, if you have a well-established filter, it's likely that it's not going to take that much to double the amount of bacteria in the filter - it's where you start from "no bacteria" that it takes 4-6 weeks to mature a filter. One of the reasons for that is that the first kind of bacteria needs to grow a large enough colony before the second kind has plenty of "food" available. When you already have a decent colony of each, it should be fairly easy to grow more of them.

Just as a precaution if you move the filter to another tank, only feed lightly the first few days. That will reduce the amount of ammonia produced by the fish, and thus the amount of ammonia the filter needs to take care of.

--
Mats

Tanks a lot

The filter from the aquarium had nine fishes, in the new one it has only four! But of course there is another filter left... same capacity...

I will feed them lightly for a few days... and test my water a lot!