I have a wp40 on my 90g
Extremely pleased with it
If the quality holds up, I will say it is one of the best wavemaker pumps I have ever seen or owned... especially considering the price. It moves about as much water (IMO) as a
pair of Vortech mp40s (!) and produces a better 'wave' than comparable Tunze models.
IMO it is not to big or obtrusive in the 90. Especially since it is strong enough to be the only pump in the tank. I have mine in the left rear corner, about 8 inches below hte waterline. and I get huge waves and flow all the way down the entire length of the tank. My water surface is 100% moving and turning over; no more surface 'slicks' where the water doesn't move enough.
But, if you are starting with a 55g, and then planning to upgrade to a 90...
I would say get (1) wp25 now, and add a 2nd one when you upgrade to the 90.
Or sell off the wp25 along with the 55 tank, and go with a single wp40 in the 90.
Because the wp40 is going to be too much in the 55g.