My P. oligacanthus and P. grandidieri pairs have once again spawned simultaneously in the same 180 G tank. They've done this before but the difference this time is that their clutches of eggs are only about a foot apart. Despite the close proximity of the two pairs, which are very effective parents, their is no conflict between the pairs. They seem to know that what's going on a short distance away is not a threat to their young. Having said that, there are other fish in there that do pose a threat (P. polleni particularly), and the pairs are very "aware" of their presence. Here's a short video of the situation.