Difference between a canister filter and a reactor.?

ok so i have a 125 gallon reef tank that i just set up and so far all the fish are doing good with the filtration of 160 pounds of live rock and a protein skimmer in the sump and chaeto in the refugium. i have a phosphate problem so people have been telling me to get a phosphate reactor but i looked up how it works and it seems to do the same as a canister filter. i have a fluval 405 that is on my 10 gallon but its only doing mechanical filtration so i can just replace it with a small filter since theres no media inside. but if i transfer it to my 125 gallon to put some phosphate media in it will it work the same way as a phosphate reactor?