Good morning tu...
Apparently, your UGF
isn't functioning well. UGFs aren't really the best filtration system. They're easily plugged with plant roots and small pieces of substrate. Filtration in general just replaces toxic water with less toxic water. The pollutants must be removed and you know that means a water change.
You can keep the UGF
, but you'll need to do larger and more frequent water changes to keep the water clean. A minimum of 50 percent weekly should suffice, that's what I do in my tanks.
An alternative that wouldn't be too expensive, would be to unplug the UGF
and leave it in the tank and just replace it with an HOB
. I like Aqua Clear. A 50 or a couple of 20s placed at opposite ends of the tank should be fine. You should still be doing the larger water changes weekly.
If you're very good about doing your weekly water changes, you could go for a 60 to 70 percent weekly change and use an Aqua Clear 30 filter. I know I'm bucking some expert advice here, but the water changes are more effective than the filters for keeping the water clean.