What is the best way to move fish from one tank to another?

The established tank's water will hardly be of any help in your 90 litre considering the water doesn't hold that much beneficial bacteria. And no matter what you put in there, you should fishless cycle anyway until you see a constant zero Ammonia and Nitrite and Nitrates are under 20ppm.

Most times, without the use of established filter media a Fishless Cycle lasts between 3-6 weeks. With the addition of already cycled parts from another tank, the cycle may or may not shorten, it really all depends on what the liquid tests tell you. Personally I'd just fishless cycle it to make sure the water is in top condition before transferring any fish.

Now, when you get to that point, if you are using the same water and the tank specifics are all the same, you can easily net the fish out and transfer them with no problems. However, since it will be a new tank you may want to use the bucket method which requires you to place all of your fish in a bucket with their tank's water and then adding small amounts of the new tank's water every 10 minutes until more than half of the water is that of the new tank. When releasing them, you net them out most times (ESPECIALLY when the water comes from a pet store. Don't let that bag water go in your tank).

Good luck, hope I helped and check out the links.

You need to let the new tank finish cycling or your fish will have a hard time surviving. Search "aquarium cycling" if you don't know how this process works because it is very important. You should add some water from the established tank to help get the cycle started. Moving the gravel could be a disaster because you would have to take the fish out of the tank they are in to get to the gravel. I think it would be well worth a few bucks to just buy some new gravel and not risk stressing your fish any more than you have to. When it's time to actually move the fish from one tank to the other, make sure the water temperature is EXACTLY the same in both tanks or have some fish bags to float the fish as you move them so you they don't go into shock also. Hope this helps :-)

If you can move gravel, ornaments or filter media from your established tank to the new one that will transplant some cycle bacteria and help cycle the new tank. Water doesn't matter.

If you are going to move all the fish, then move ALL the stuff from the 25l.

Just run the tank for 24hours for things to settle. Unless you are going to do a full fishless cycle on the new tank, running it longer makes no difference. If you are going to "clone" the cycle from the small tank, move the media and fish in together.

Ian

A 29gal aquarium isn't sufficient for even one oscar to stay comfortably, not to point 2 with different fish. a ten gal is even worse. you need to the two get a one hundred gal for all of those fish in the different case get a fifty 5 gal and do away with all yet one fish. seem up your fish... oscars can get a foot long. i understand dempseys get vast, yet i don't remember how vast precisely. and that i don't understand with regards to the midas. something desires to be carried out in the different case your fish will finally end up lifeless.

you should put the fish in a bag with water&dip the bag(with fish) into the new water and wait for the temperatures to combine, then release the fish so that the temperature of the new tank doesnt shock the fish. you could also transfer gravel or any other decorations from the old tank to the new one, just make sure they're clean first.

Let the filter run for a day, then use a cup to scoop the fish out of the first tank into the second one. If they're really small fish (like tetras) you want to do the bag technique you did when you first got the fish

Hope it helped

ya the more stuff u take from the old tank the better, rocks, water for sure, and gravel holds bacteria u want that.

and make sure the tank is Oxygenated.