I agree with Mike. DSB
, and Macro.
As for Species, I have a few favorites. Chaeto, obviously, Halymenia, Gracilliara, and Grape caleurpa.
The Halymenia is very pretty, and the Gracilliara can be too. Both are fish edible, so you can feed some to fishies when trimming. Grape Caleurpa has not gone sexual on me yet, and it grows like wildfire, which makes for good nutrient export.
Mine is also on a timed lighting schedule. About 10 hours.
To clarify on lighting and going sexual, there are a few Macros that tend to go sexual more often on certain lighting schedules. C. prolifera is one of those.
And it's less a matter of "releasing toxins" when going sexual as it is a matter of releasing excess nutrients. There's nothing inherently toxic about what the Macros absorb, but if the entire plant dies and releases it's lifetime worth of absorbed nutrients, it can cause serious water quality issues. Also, you don't really want spores landing all over the DT!