Cleaning Up

go to a petstore and get a gravel vaccum. Siphon the water out of the tank, while cleaning the bottom with the gravel vacuum into a bucket. Take out the filter media and rinse it off in this bucket of dirty water. Then with a second, brand new bucket you fill it up and refill it with new water. Treat the water with chlorine/chloramean remover first. I dont have chloramean in my water supply, so letting the water sit for 24 hours lets the chlroine dislove. Or there are systems called pythons that allow you to empty the water right into a drain and refill it with the same tubing, so you dont need to use buckets.

Definitely need to be using a gravel vac if you aren't already. Do you do weekly water changes? or any water changes at all?

If you use your gravel vac each week to remove the old water for the water change, it will help keep the gravel cleaned up better and you can also use it to suck up any debris that lands on or around plants, driftwood, rocks. For general maintenance changing around 30% of the water per week is usually sufficient. Don't be afraid to do multiple, larger water changes if needed to remove more debris.

Also, don't replace your filter cartridge unless it's falling apart. The majority of your good bacteria you need lives in there. If it gets gunked up, you can just swish it around in old tank water you siphoned into a bucket to clean it up, then just put it back in there. I clean mine every month or so as needed and only replace them maybe every 12-18 months or longer probably sometimes hehe

Excellent advice above, but let me chime in with something else that needs to be said. If your tank has accumulated that much grime in a week's time you are probably overfeeding your fish. Your gourami only needs a very small amount two or three times a day to be happy. It is very difficult for many newbies to resist feeding their fish every time it "begs" for food, but you must if you want a healthy tank. Remember, your fishies stomach is only about as big as its eye, so that should help you in determining how much is enough.

Good luck!