transferring two tanks into 1

[ImpendingSquid]

I have a 5-gallon and a 3.8-gallon tank, the 5-gallon has been running for a year and is good but the 3.8-gallon tank has only been running for about 5 months now. It is already showing coralline algae and all that good stuff but I'm moving to college. They only allow 10 gallons and below to be accepted in the dorms. I plan on buying an 8-gallon tank. My question is how does the transfer between both tanks into 1 go about? I plan to transfer 2 small rocks from my 5-gallon and 1 rock from my 3-gallon tank + the sand.

How bad of a cycle will I get for the new tank? I'm just planning to add the sad + rock from both tanks into that new tank but is that safe to do?

I'm scared that because both the rocks + sand are different everything is going to die. I do not have anything type of hard corals. Mostly soft. I'm just scared of not knowing what to do. There are forums here but they all have a jump to like either 20 to 120 gallons tanks that they transfer to, while in my situation is just a small jump or not even a jump.
I'm at a loss, I wanna combine both tanks, I'm scared the new water will kill everything. Do I combine both waters? Do I put new water first then rock and sand from both tanks? I just need help and clarification. Thank you

 

[Asm481]

You are over thinking here. The water has very little value or consequence. Might give a little nitrate or phosphate which we want a bit of. So add all the rock and sand you want, add whatever water that doesn't look to messed up then top off with new water. Soft coral are very forgiving, they might shock a couple days but light and flow they will come around.

 

[ImpendingSquid]

You are over thinking here. The water has very little value or consequence. Might give a little nitrate or phosphate which we want a bit of. So add all the rock and sand you want, add whatever water that doesn't look to messed up then top off with new water. Soft coral are very forgiving, they might shock a couple days but light and flow they will come around.

Thank you for the reply. I was just afraid that since both the waters, sand, and rocks are different it might set off a nuke. For the water do I just make new water or do I combine both waters and put in the sand and rock then put the corals, fish, and inverts?

 

[Asm481]

With the small size you have I would use new sand with your cycled seasoned rock. (Do not let the rocks dry at all). Use what you can of your water so you get some of your existing nutrients adding new well mixed saltwater add my critters and call it a day.