Upgrading 20gal to 75gal -- Possible to do it in one go?

Hi!

I have a 20gal tank that is up and running and has a baby black ghost in it. In the short term I plan to move it asap to a new long 75 gal tank before it starts to grow. (I know 75 isn't ideal, but seems like a long one would be suited as the fish doesn't use much of the verticality it might in say a tall 100/150 tank -- and I can upgrade later)

Logistically, the 75 gal tank would go onto the stand where the 20 gal tank is sat. So if I wanted to cycle the 75 first, I'd also have to move the 20gal in order to make way.

What I wondered was, would it work to e.g.

* Drain the 20 gal into buckets and put the fish in one of them. Position the 75 gal and transfer the substrate, rocks and plants, along with the 2 HOB filters I have on the 20. These would sit alongside the new tank's filters.
* Put the water from the small tank into the new tank. Immediately place the fish in the new tank. Top up with dechlorinated water once it's settled.

Even though the tank is bigger, given that the bio load isn't changing, would the transferred filters mean it's essentially cycled -- and then over time the bigger, new filters would pick up the bb?

--Sam

 

What kind of media is in the HOBs for the 20?

 

It's 2 Aquaclear 30s. I have some sheets of filter floss first in place of their filter inserts and then bags of Biomax on the way out. There's also cylinderical sponges on the filter inlets.

This was them before cycling (I removed the polish pads in there as it did start to back up once we were up and running)
https://www.fishlore.com/aquariumfi...gal-tank-side-by-side-ok.527090/#post-5193113

 

You could do it 3 ways.

1) Just like you said. With 4 filters running. May be too much flow for the fish?

2) Take ALL of the media and pre filter sponges and put it in the new filters. Dont stock and keep an eye on it for at least a month.

3) Put all the media in the new filters and just run floss in the 30s to catch crud from moving the substrate. That way you still have all the filter film from those filters.

 

On the day you want to move, take everything out of the 20 put the 75 g in place and fill it with everything from the 20 plus what every else is required, not a problem.

 

My plan was to use two Tidal 75s in the 75 -- but perhaps to get it up and running, I could use all the media from the 2 30s to fully load one of the 75s and that would be enough with the single fish in there to kick start things? Then if things remain stable I add in the 2nd 75 -- I'm not 100% on the science, of whether 2 75s would split the filtration between themselves or if it's always additive, so a 2nd 75 with fresh media wouldn't necessarily detract from what is going on with the established media?