Complex sentence: Some fish keepers have trouble housing plecostomus in heavily planted aquariums, some plecostomus thrash their tails to develop a "well" in the gravel of the aquarium, making it is often necessary to replant aquarium plants that they dislodge.
Split into simpler sentences: Some fish keepers have trouble housing plecostomus in heavily planted aquariums because some plecostomus thrash their tails to develop a "well" in the gravel of the aquarium. It is often necessary to replant aquarium plants that they dislodge.