Placing a bag of AC next to a pump intake actually allows faster filtering than using a "reactor". Make the bag of bridal veil material loosely bunched and tied together so it can lay acros the intake. Buy the Bridal Veil/Tulle material with a mesh fine enough to hold the AC but course enough to allow easy water flow. It's available at the fabric store in different mesh sizes for about $1 per yard.

 

FYI, that word, reactor, is a marketing ploy. It does nothing more than what you suspected. There is no special "reaction" going on. It's just an activated carbon filter.

 

Water changes are a lousy way to reduce N compounds (Ammonia, Nitrite and Nitrate). Think about it. You do a 20% water change. That dilutes the N compounds by 20%. If the Nitrates are 50ppm before the water change, they are 40ppm after the change. That's a ridiculously insignificant decrease.

A much faster and more effective way to reduce N compounds is to leave the lights on 24/7 making the algae grow 24/7 thus doubling it's speed of reducing all Nitrogen and Phosphate. Add a bunch of macroalgae to eat up more N and P. In my experience, the algae that occur naturally in the water and on rock and glass, plus a little macroalgae can drop Nitrogen by half in 24 hours.

 

Carbon does not have any effect on Nitrate levels.  To reduce nitrates you need to grow macroalge, do a water changes, or just slow down until the natural biological filtration catches up to the level  you are stocked at

 

Thank you!

Arthur