2 solutions:

1. Put your fish in a smaller tank so that you can cycle the 5 gallon tank. Replace the gravel with sand, and plant accordingly.

2. Get rid of the gravel, as it traps food and feces extremely well, even with vacuuming. There are three options for substrate, the best of which is to have none at all and to have only free-floating plants like Java moss, Java ferns, and anacharis. Second is to go very easy with glass marbles - don't even cover the bottom of the tank, just for decoration. Again, utilize free-floating plants. This is probably the least favored option. The happy medium would be to use aquarium-safe sand and use that as your substrate for your plants. Do a 100% water change every 2-3 weeks with a full tank breakdown. Otherwise, your tank will cycle, with possible bad results for your fish.

If you identified the anaerobic bacteria on smell it should smell like sulphur or rotten eggs. I only had this happen once when I had an artificial rock that was hollow.Gravel had gotten pushed inside and settled. Since it was never vacuumed when I removed it(used it to seed a new tank and didnt like the look as it faded)It reeked like sulphur. A micro gravel is best for aquatic plants that root or will root in substrate. A siphon type gravel vacuum will remove the detritus and is easy to use once you get the hang of it. If your heavy planted then just hover over the gravel to remove fish poop and debris. Every 3-6 months uproot and gravel vac 1/2 the tank thoroughly, then the next week do the same with the other half.

Some oto cats in a planted tank are a great addition. They will eatup some left over food as well as any algae on plants and glass. They are very small(max 2 inches long) and dont add much to you fish load. Also try not to overfeed.

I know I'm not overfeeding-I watch him eat what I give him, which is never more than 4 or 5 little pellets a day. And I do gravel clean every time I do a water change-that's the only way I get that stench, yes, the rotting egg one. I really like my plants that I have in there-a thriving sword plant and banana plant, so I do not want to move to being gravel free. My hope was that this was a common problem in tanks w/out undergravel filters. My betta seems to be thriving. I just know his water stinks when I gravel clean.

Gravel size and depth is a concern, so, How deep?, and approx. size of gravel or brand name ? I have densely to moderate planted tanks some just plant only and have not had this problem except for the rock thing. The sword deffinatly needs gravel (heavy root feeder).