My tank is 120g. It has been up and running for 6 months...what I am finding out...Blyxa Japonica grows very well for me and I am wanting to continue it towards the left side of the tank as well...basically carpeting the front with it. At this time I have never had any bottom feeders and was thinking of adding some Cory's. Would Cory's work well in a tank where the foreground is B. japonica?
I think cories would be just fine in your tank with your plant selection. Cories are my favorite fish. Just remember cories have zero respect for boundaries or territories, so territorial fish tend to chase them a lot. Very nice tank by the way.
My Cory's did well with a fully carpeted tank (Blyxxa, S.Reps, Downoi, Glosso). They were alive and seemed happy. When I removed the Downoi to create a bare substrate area to feed them in a cleaner way, they gravitated towards that area. They seem to love sifting through substrate. I just glanced at my tank and all of my Cory's are at the exposed substrate area of the tank. the area only takes up maybe 3-5% of my tank floor in one corner.
I removed the Downoi and transported it to a new tank only a few hours ago.
Lovely tank !
Cories (other fish too, for that matter) will thrive as long as they have approx the right water conditions and are given the opportunity to exercise their normal behaviour. Sifting/pigrooting through the substrate is a very important part of their feeding behaviour. They sift, rest and sift some more. So please do not totally carpet your tank if you're going to keep cories.
Substrate should also have a sifting-friendly grain size (around 20/40) and consist of rounded grains that will not harm their gills and barbels. Substrate should also be kept clean.
Based on available open ground space, I'd say 8-10 medium sized cories would be ok. In any case, never less than 6 cories !
You could also go for a larger flock of one of the dwarf species, like habrosus or hastatus. The idea behind this suggestion is that dwarf cories move more about in the water column, so utilize volume better. They are also fun little guys to keep and observe