What type lighting and bulbs do you have? Also what type of crypts? There are many types of crypts with some growing quite tall like Crypt Balanese. You might, depending on your lighting be able to grow Water sprite, Wisteria, or Hygrophilia corymbosa.
yes they are low light i have them in many of my tanks low and high with no co2
There are a couple Rotala's that can handle lower light but mostly Ludwigia's, Cabomba, and most Rotala's, if they grow at all will grow tall and lanky trying to reach the light. They also will not reach their full color potential unless they are a green variety. I grow all of these plants and many different types of them in various lighted tanks and have for many years and I can say mostly with a couple exceptions do not grow well if at all in low light tanks.
Just what are you considering low light and which ones are you growing?