Personally, I would pull out the Peppered Corydoras and then add the dwarf cichlids.
Why? Because I'm a strong supporter of temperate fish being kept in a temperate tank, where the water temps change through the seasons. Peppered have been officially recorded in 15C water and I recently (wish I had bookmarked it) came across a post where someone let their Peppered get a winter cooling period of 10C with no harm at all. I also wonder if the sheer size of Peppered may be spooking your Kuhli Loaches, a 13 group ought to be quite active.
The other alternative in my opinion is to choose a more appropriate catfish group that will do well at the ~24C+ temp you will need, especially after adding Apistogramma, for instance Corydoras sterbai.
I'm not interested in pulling the corys, they seem really happy, and are not having any problems that I can see... When i was having health issues, they were the only ones not to get sick, and have been laying eggs regularly from the beginning. I've only lost 1, and that was a few days after i first brought them home.
What kind of lighting do you have? Do you ever use liquid ferts or root tabs? Floating plants can help a lot with fish security, but if you already have low light it would be even harder to grow plants down there if you added floating plants. Probably a few would be OK.
My lighting is what came with the tank originally, 2 18" 15W bulbs. I'm not sure how i'd go about increasing the light. I'm not that great at doing these things myself. I use root tabs, but i haven't used liquid ferts, as i was told that with low light and no co2, i didn't need it.
You could also look for a couple of taller pieces of branchy type driftwood and replace a few of the shorter ones - that will add some more depth/visual interest, too. Also, you could get some river-type rocks and do some piles. Then you could put some java ferns/anubias onto the top of the pile to add different heights, and make the bottom look less flat, if that makes sense.
I haven't been able to find any branching driftwood in any of my lfs, they all have small pieces, or really huge pieces. i've tried to change up the height by standing a few pieces on their end, but it's not quite what i want. i'm not comfortable buying wood online, as youreally cant tell what it will look like until you get it. I'm also not a fan of the look of rock piles. good idea though.
To keep the floating plants where you want them - go get some of those little suction cup clips to hold airline tubing. If they're a full circle at the end you can clip the middle and then put the stems of a few of the plants through them. They should hold them in place, then for me, I kind of layer other plants slightly over the anchored ones to keep them there. I used to have the same problem - they would circle around and clump together in one corner until I did this. Works like a charm!
I like this idea, and will do so asap!!
any taller low-light plants that you can suggest? I have some fairly new Vallisneria plants, which seem to be doing ok, not great but ok.
Thanks for the advice everyone, any more will be appreciated as well! I Figured the apistos weren't a good idea, i just really wanted to get them.
Go me for not impulse buying!!!