I just bottled today. Here's a photo of how high the krausen got up to.
View attachment 76261
That's a bit of a shallow one. Normally it's probably twice the height (this was liberty bell, 1.053 OG). So it would probably reach the 25L mark. So in theory a 26.5L fermenter would be ok for you, but close. The 30L one has plenty of headroom. Though as you can see the actual capacity of mine is a few liters above 30, so you'll probably be fine.
Additional things with my one:
Good things
- Good quality construction.
- Handles and clamps make it easy to work with
- Bottling spigot is at about the right height, though could be a little lower. I lose about a pint to a litre of beer every batch
- It has a rotating racking arm (bent tube on the inside) that means you can pick up from just above the trub layer, but in practice it always points fully down and is still clear of the yeast cake (see above).
- Stable. You can in theory stack multiple on top of eachother, but I only have one
- Legs are adjustable
The bad:
- The inside of the legs are sharp. This is the only bad party of the construction. Though it's easy to sand them down to make them less sharp
- The rubber on the bottom of the feet is beginning to wear down.
- The legs are just u-shaped legs. If you ferment inside, it may damage the carpet or a soft floor
- There's not quite enough room to get a standard bottle under the bottling tap. Shame, but easy to work around. I bottle over the sink, so it's not a problem.
- It's not quite short enough to fit on my worktop and below the wall cupboard, which is a shame, but isolated to me
Hope that helps. Overall, very happy with it. Would buy again