lol yea it's a tad oversized. I honestly think you should see if you can return it and get your money back. I have had soooo much trouble with those cheapish wavemakers, either they just fully die or either the plastic mesh around the fan breaks off and stops the fans from spinning. I think in my time ive gone through probably 6-8 of those wavemaker and only successfully had 1 last a few years. I eventually gave up and bought a couple of mp40's and now it's all perfect
.... which may be a tad overpowering for yours as well.
With the ebay wavemakers, I've tried different controllers to slow them down..... no luck on any, also tried building a few things myself to control the flow a little and had little luck, only been able to setup successfully an auto switch on and off function but the noise they put out when flicking on and off does my head in so gave up on them...... you may have better luck but that's my personal experience.
maybe just try and return them and get a smaller wavemaker or if you cant.... just cut your loses and look for a smaller wavemaker