There are several variants of Bolbitus that i have kept over the years. One that had very thick rhizomes, tall stiff "stems" that would reach the top of a 22" high 125g tank. The leaves were very erect. Folks from the Northeast may remember this plant. I originally obtained mine from Karen Randall in the early 90's. Also know to aquarists in the BayArea; it was frequently offered at the SFAS auctions during the late 90's. (Maybe it is not even B.heudelotti!).
There is at least one other variant which has more delicate rhizome and stems; its leaves tended to bend and sway with the current. I seem to recall that it only grew 6-10" tall. I obtained this much smaller plant in the early 1980's. In the same tank, it never grew as large as the "tall" variant. When i sent some to Karen, I seem to recall learning that it was uncommon among the NEC crowd. Since then this smaller variant has become relative common. Probably more than one clone. Unfortunately, i lost mine during my recent move.
I am looking for some of the "small" variety. Of course, as with most plants, environment can also change morphology, but only to some degree. We know how variable are Java Ferns (Microsorum). No reason to believe that is not also the case for African Water Fern. I dont think it has received nearly the same attention.
Most likely many imports of Bolbitus have occurred over the past 25 years. I am trying to figure out how many variants may be circulating and how much a factor is aquarium environment.
APC's plantfinder lists it at 18". Lets hear how tall are the Bolbitus that you currently keep. If possible, please provide pictures of the entire plant, its leaf shape lying on a piece of white paper and changes you recall since you acquired it. Also helpful is the shade of green (some are very dark) to further help document the different versions. Finally, try to remember from who you obtained the plants to help establish the lineage. Tank conditions would be helpful, but I can't guess what the most important factors might be (KH&GH?). thx, Neil.