Hi,
new to the forum sorry if this is talked about a lot i didnt see it as a topic.

I bought a 125 gallon tank yesterday and after i build a stand and get it all together im looking to transfer fish in about 2 weeks.

My plan right now is to change from gravel to sand too, i am worried about cycling the tank and losing my fish.
The basic plan is to change my filters today or tomorrow and save the old ones so i have the extra bacteria and place them in the water of the new tank. I am going to run the tank for a day or two before putting the fish in them but, without fish its hard to grow the bacteria. I also plan on putting about 5-10 gallons of dirty water from the 30 gallon into the tank.

Is all of this a good idea is there something i am missing or something i should not be doing?

i really cant lose these africans and worried about the transfer please help!

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Tank
125g african cichlids making it work
75g rimless Reef in progress

I recently transferred all my fish from my 29 gallon to my 75 without any issues, but the 75 gallon was already established and had fish in it. I would imagine that even if you drain your 30 gallon completely into the 125 gallon, fish, filters and all, you will still have cycling issues for the simple fact that there is 4xs the water volume in the 125 tank. If that is the route you decide to take then I would suggest you keep a very close eye on your water parameters.

Also, If you are only planning on transferring 5-10 gallons of water to the 125 remember that amount of water in a 125 tank might cover the bottom of the tank up to 2-3 inches at best.

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75 Gallon Planted

I recently transferred from a small tank to a small mid sized tank (10 - 40) so it is not the size of your move but proportionally it is.

Since my new tank was going to the same location as the old I had to do the swap in one day.

I drained water from the tank into a large bucket, included some plants/decorations, etc for the fish to hide under. I placed a heater into the bucket to keep it to temperature, an airstone and then covered it with a towel to keep it dark.

I placed the filter media in a bag to keep it wet with tank water.

Moved out the old tank and in with the new tank. (made sure everything was level, etc)

I added a bit of prewarmed water to the tank, rinsed the new gravel/decorations, etc and then added them to the new tank. Transferred the old decorations which remained wet in the old tank water. Then took the old gravel and spread it on top of the new gravel and then filled the tank up with pretreated water that was already to temp and set up the new filter and began running it and I also setup the old filter on the other side of the tank. Did all the tests on the water. Waited a couple hours and tested the water again.

Then with the tank lights off I added the fish and kept the tank light off for the rest of that day.

Tested the water again that night and again in the morning and then went to testing daily for the first week, every other day for the second week and am now back to a normal schedule. The readings have all stayed at 0 except for PH and high ph.

We waited a week or two before we added any additional fish and then added them slowly (5 - 7 days) and only 2 or 3 at a time.

It's only been about a month or so but the tank so far has no appearance of recycling. Other than a small fish being sucked into the filter and a new one dying we have had no issues at all.

Thanks that was helpful. what was the purpose of keeping the lights off? just keeping them less active and not so stressed?

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Tank
125g african cichlids making it work
75g rimless Reef in progress

Would you be opposed to taking all of your gravel and putting it in there and then placing all the sand on top of it? It would fully cover it and it probably wouldn't be seen. If you did that and didn't increase your stocking level for a little while, then I think your cycle issues would be minimal.

Using any of the old water from your other tank is useless and you'll get nothing from it. Just put in nice, fresh water.

To cut down on the stress. After advice from here I do that when I drip acclimate new fish and it really seems to make the transition easier for the fish.

If you want to do sand and not gravel stick a bunch of the gravel in a nylon stocking or some sort of bag like that and put it in your new tank to transfer the bacteria. I'm not sure how long you should leave it in for, but a few weeks would probably be sufficient.

gravel in nylon is probably the way im going to go. hopefully those filters + decorations and that will be enough ill test every day and act accordingly thou thanks every1

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Tank
125g african cichlids making it work
75g rimless Reef in progress