I was searching for mesh to filter my intake fans after seeing @Wolf1 with mesh on hers and found this super convenient self-adhesive mesh. It’s meant as a patch for large screens, but at 3.5 inches it’s a perfect fit for our Grobo’s fans.
https://www.amazon.com/gp/product/B073QWL2DH/ref=ox_sc_act_title_2?smid=A1G491DNVW3K0&psc=1
I’m a he 
and for .89 cents a piece not bad at all
Whoops! 
Interesting idea. You put it on the back of your fans assuming?
Yeah, it helps prevent dust from being pulled into the grobo through the intake fans.
What screens are these? Where did you get them ?
I got them through newegg. Unfortunately it looks like they are out of stock. All you need to look for is a magnetized 140 mm dust filter. I included a screenshot of the ones I bought. My order came with 4 in the package.
You may be able to find a magnetized filter that is bit enough to cover both fan intakes, the 140 mm x 140 mm are big enough to cover one fan intake.
On a side note you can make your own if you have a 140 mm dust filter. All you need is some magnetic tape like this. The tape doesn’t need to be 1/2" wide.
Do these filters reduce air flow coming in to the Grobo is my concern?
The mesh on mine isn’t too fine, so it is unlikely they will restrict airflow very much. If I had a wind speed gauge I’d test it.
If you are adventuresome, you can probably replace the fans in the Grobo with higher quality ones that push more air.
There are many options on amazon with magnets attached. Currently running these, I have dogs so the finer mesh was a must. I don’t have any way to scientifically gauge it. However, I conducted a simple “feel” test when I installed them and could not feel a difference. Also temperature and RH was unchanged.
Thermaltake 120mm Black Magnetic Fan Filter (AC-002-ON1NAN-A1)
https://www.amazon.com/dp/B00KHO0I38/ref=cm_sw_r_cp_api_i_nAt7EbJZ7T8W0
I like that idea of replacing grobo fans, may venture into that in between this grow and the next.
Is the filter inside the Grobo? What is it for?
Outside the grobo, placed over the intake fans to prevent unwanted debris from getting sucked into your grow space.
Interesting!
NZXT makes some really good fans, I’m running all NZXT fans in my desktop. If you have an old computer you can connect an NZXT hub to it and control the fans with it. I haven’t done any research yet, but it might be possible to use Linux or Raspberry Pito control them. I’m sure their API isn’t too complex.
Won’t let me post any links, nzxt dot com and look up the cooling and accessories.
Here’s a screenshot of their fan controllers.
You can put it inside or outside. Putting it on the outside will also help keep the fans clean.
That’s perfect 
