Transferring betta from 3G to 25g

So I rescued this betta from Facebook a few months ago. He was in a small tank and looked sick. He has grown into a healthy looking boy. I have him in a 3 gallon tank as that’s all I could find at the time. I have this 25gallon tank setup it’s been running for a few months with a filter and heater but there’s been a bunch al algea in it and I have had to do a lot of cleaning. I want to move my little boy from his 3 gallon tank to the 25 gallon tank but I don’t know how to go about it. The 25g tank has 0ammonia 0nitrite 0nitrate. Would it still be considered a fish in cycle if I move his current filter and decorations into the big tank with him? I added his before picture.

 

Is that last photo the new tank? If it's been running for months with plants, it's ready for your fish. To be careful, you can dose with Prime when you move it in case there's an ammonia spike and check your water for a few days just to make sure, but I think you won't have a problem.

 

Is that last photo the new tank? If it's been running for months with plants, it's ready for your fish. To be careful, you can dose with Prime when you move it in case there's an ammonia spike and check your water for a few days just to make sure, but I think you won't have a problem.

Yess that’s the new tank

 

You're good to go.

 

If you move the fish decor, filter, heater, etc. that will keep the beneficial bacteria from your current tank and move it to the new one. As kansas said, have some Prime on you and keep an eye out for any ammonia spikes but you should be okay. I would monitor it for at least a week just in case.