A normal HOB and Airstone are not going to make so much current that anabantids are off the table. If you really want a Betta or Gourami, get it. Avoid settling for something you don't want; that just makes you unhappy with your tank...
If you have really cranked up the flow with a specialized or super oversized system, then you might want to skip them, but you can still get other riverine species. Cherry Barbs are beautiful. White Mountain Cloud Minnows are another option you did not mention.
Second, avoid the pleco. A 55 gallon tank is still too small for the common pleco. It gets big, and it gets there fast. Some species stay smaller, but are messy and stay hidden all day. They just don't work out very well in most tanks.
If you REALLY do have the flow and highly oxygenated water, and you want something different, look into the Hillstream Loaches as your bottom dwellers instead of a pleco. They are a more advanced fish, with special care requirements. They are sometimes labeled as some variety of Asian Pleco. The Reticulated is the most visually stunning.
Convicts are colorless grey drab fish. However, the cichlids can be a very nice centerpiece fish. Try to find ones that stay under 4". With the Apistos or Rams, you can have several in a 55, or a pair, or a single fish. Same with Kribs. A pair of Angels would work, or a single fish. All will protect a nest, but they only chase about a foot.
Other small Cichlids will work, like Jewels or Firemouths... but get only one. They can become murder machines when they spawn.
Finally, the common redtailed shark could be what you are looking for if the above options don't pan out. Avoid including the pleco, but they will coexist happily with the loaches.
If you have really cranked up the flow with a specialized or super oversized system, then you might want to skip them, but you can still get other riverine species. Cherry Barbs are beautiful. White Mountain Cloud Minnows are another option you did not mention.
Second, avoid the pleco. A 55 gallon tank is still too small for the common pleco. It gets big, and it gets there fast. Some species stay smaller, but are messy and stay hidden all day. They just don't work out very well in most tanks.
If you REALLY do have the flow and highly oxygenated water, and you want something different, look into the Hillstream Loaches as your bottom dwellers instead of a pleco. They are a more advanced fish, with special care requirements. They are sometimes labeled as some variety of Asian Pleco. The Reticulated is the most visually stunning.
Convicts are colorless grey drab fish. However, the cichlids can be a very nice centerpiece fish. Try to find ones that stay under 4". With the Apistos or Rams, you can have several in a 55, or a pair, or a single fish. Same with Kribs. A pair of Angels would work, or a single fish. All will protect a nest, but they only chase about a foot.
Other small Cichlids will work, like Jewels or Firemouths... but get only one. They can become murder machines when they spawn.
Finally, the common redtailed shark could be what you are looking for if the above options don't pan out. Avoid including the pleco, but they will coexist happily with the loaches.