Not really. Those flow numbers listed are always the theoretical max output of the pump pushing water by itself. If there is any restrictions, such as media in the way, then the pump is going to go slower, thus less flow. Usually, the true flow rate on a filter is usually half or less of the stated flow rate. Rule of thumb I was told and use is to take whatever flow rate is listed and use 40%-50% of that number. So a canister filter with a 370gph flow rate is going to have an actual flow rate of 148-185 gph usually when filled with media. (more restrictive media will have less flow)
Typically, you want to turn your tank at a minimum of 3 times per hour. So you take 180 gallon tank and you'll want to be moving 540 gallons per hour at a minimum. Some advocate more. I have a friend who swears by 10 times the turn rate. You really don't need THAT much flow in my opinion.
So if you are using the 303/403/CF-400 models of the sunsun/aquatop filters then you are going to need 3 of them. If you are using the 304/404/CF-500 models then you are going to need 2 of them for a tank that size.
many thanks. I will see about getting a second filter...problem is with space
Tonight I will try playing around with the materials some more...got some of the pot scrubbers from local supermarket...will try these along with carbon and ceramic rings and see what gives.
also I think I will be doing 2x per week 50% water change till I find a solution...maybe a HOB kind of filter or reintroduce one of the old DIY filters...