Hi Greenmagi,
I have a 75g Seaclear II with wet/dry trickle filter built-in to the back. When I first set it up in Dec 2004, I planted it and did fishless cycle - since then I have always measured 0 amm/0 nitrite/0 nitrate, doing about 5% water changes weekly. I have 160 W and have experimented with
DIY CO2, up to 4X2L and trying different reactor methods, but have not seen any effect on plant growth with or without it (due to some secondary buffer in my tap water, I haven't been able to get confident measurements of
CO2 concentration, but I doubt I've ever reached above ambient, which I at least partly blame to gas off from the trickle filter.) Surface agitation is very low. My vallisneria and water sprite have done great, rotala and crypts ok, but ambulia and wisteria have not done well.
I don't have any experience with cannister filters but I think any benefit you might get from the potentially higher biofilter capacity of a wet/dry filter would be redundant with the healthy plant growth of a high light,
CO2 tank. So I think I would go with cannister for a high plant,
CO2 injected system. One nice thing is my wet/dry filter needs essentially no maintenance - I rinse the pre-filter floss every once in a while when I feel like it, and that's about it.
Now,
AFAIK many Mbunas will eat your plants, so along with the issue of higher pH (I guess you can acclimate them to a somewhat lower pH than natural, but I assume not too much), you may have a tough time growing a cool plant aquascape. I have not seen any heavily planted high light,
CO2-injected East African cichlid tanks, but I'm sure there's someone out there doing it. So in your case, setting up a sump with wet/dry filter and planted refugium might be a really cool, innovative way to go. If you use floating plants and semi-aquatic pond plants, then
CO2 won't be an issue.
Ryan