looks like a proper 25mm.
If you want to go with a pre-configured kit your choices you have a a few good options - and you can determine which is best by the amount of flow your return pump will deliver.
These suggestions are based on one return pump providing flow to both outlets - after any head loss
here goes:
600-1,000+ GPH - Singe 1/2in RFGs on both sides
You'll need two of these kits - one for each side. At the upper end of the low suggested will be super punchy wave-maker like flow and will easily move the entire body of water - you probably wont even need a power head. At the lower end, they will still be pretty good and suited for a softy or LPS tank.
You may be bale to use the included 2025-050 Multidapter to plug right into the outlet. If not, then you'll be able to use the other include adapters (2021-050 modular hose adapter) to connect to the stock push in fitting - either way this will work.
You may or may not want to add some additional
1/2in Loc-Line for for some added adjustability. If you do - one stick should do it - you would split it in half and use 3 segments on each side
800-1,600+ GPH - Singe 3/4in RFGs on both sides
As before, you'll need two of these - one for each side. for this size tank these may be physically a little bit large. But, if your pump is at a near the upper range, these would be a nice broad and wave-maker like flow.
This size at or below the lower end of the flow suggested would also do really nice for as freshwater tank.
1800-2,000+ GPH - Dual 1/2in RFGs on both sides
if you want to get real crazy with it - you could do dual 1/2in on either side . I personal wouldn't suggest it, simply do to aesthetics, but that's just me - i like a super clean look. BUT, if you really want to get things moving, four 1/2in RFGs with a supply flow of around 1800-2000+ GPH would do the trick.
you would want to add a few more segments
1/2in Loc-Line for for some added adjustability in this case
If you have any additional questions, let me know.