BigIan.
just my 2p...
I remember your thread about the halted cycle, and i mentioned that i had the same problem with the plummeting PH. Im pretty sure that it was the nitrates, or at least something to do with the fishless cycle, because since i have added fish and kept the nitrates at an appropriate level with water changes, the PH has been fine, so I wouldn't worry about that aspect of adding the fish.
However, i do share your concerns about adding the fish and getting it all right.. I was the same as you, but unfortunately with good reason. I have had a number of issues:
The first was my choice of fish. To be honest I think i was confusing a mature tank with a cycled tank. YES, it is important not to use fish like Panda Corys for cycling the tank, but a tank that can support the entire bio-load due to the fishless cycle, does not mean its a tank that can take Panda corys yet. I was unaware (damn my research) that panda corys were the more fragile ones, and unfortunately i have lost 4 out of the 6 that i bought, which is a shame because they are great little fish. So whilst people are correct about its ability to support a bio-load, it cant neccessarily support the fish in question, as there are other considerations as to what constitutes a mature tank.
Now.. don't get me wrong, the fishless cycle thing really does work. My stats for the first week or two were spot on. However, after the initial period, i did have a day or two where i had a tiny rise in nitrates or ammonia. Im not totally sure why this is the case, but i have lost other fish too. I have lost 2 female dwarf gouramis (which are prone to bacterial infections, so this is difficult to say if they would have gone anyway). More importantly to your message is that i have lost two Angelfish. Annoyingly, i just cant seem to figure out why. The only thing i can put it down to is that I understand they also like a "slightly more mature" tank than a just cycled one.
MY LFS (a good one) recommeneded that i let the tank settle for about 4-5 weeks before adding any more fish, and get a good period under my belt where the stats have been conistent and good. My remaining cory's, male dwarf gouramis, and seven pentazona barbs (pretty hardy things) have been doing great now. The major change i have made is not to rely on the Juwel internal filter. To be honest i didnt really trust this thing, so i bought an eheim 2026 a little over a week ago, and the water quality is visibly better, and the stats are still spot on.
So my question to you would be to ask how good your filtration is, as this is key. Its my own opinion that good filtration is key to helping a new tank settle in and find its feet. New tanks seem to have issues, hence fish requiring more mature tanks in some cases.
I think you are doing the right thing with holding back on the Panda corys, but i also thing that it may be worth waiting a while for the Angelfish too. However, I also understand your dilemma, which im afraid i can't solve. If anglefish are the main fish for the tank, and you don't want fish that you arent going to keep, then how can this be done.. hmm... not sure... also.. if a reasonable percentage of the fish are not added in the first go, then the bio-load may drop back.
Im keen to find out now (for me) how adding a few fish onto a 50% bio-load affects the tank, and how much of a mini-cycle will be caused if any.
Anyway, sorry for the ramblings of a newbie.. not sure if it will help or not, but its just my experience..
Cheers
Squid