no way for severums, and personally i wouldn't go there with angels either. there is just absolutely not enough space in a 75g tank for 6 or more of those species. severums reach at least 8-10 inches when mature, older males can hit a foot. the author says "you wouldn't put 50 inches of oscar in a 50g tank" but then is recommending 60-72 inches of severum in a 50-100g tank. as far as being planted, who cares if you bury the roots. severums will still try and rearrange the tank to their liking. even if they don't eat the plants, they may still pull the leaves off of them. i have silk plants in my tank with severums, and i see them everyday trying to yank the leaves off. the edges of many are frayed. it's not because they're hungry, it's because that leaf happens to be blocking their cave or is in the way when they swim or they just don't like it because it looks at them funny.
the pecking order thing DOES work, but it only works in a large enough tank for the size of the group. it doesn't reduce the aggression that is already going to be present, it spreads it out enough so no one fish gets the brunt of it. in a tank that is too small, aggression gets worse because there are not enough territories for each fish to claim as their own. instead of having a peaceful tank, you have a tank where the weakest members are killed until there is an appropriate amount of space for all that are left. then they may calm down and interact peacefully. either three severums in a 75g (with somewhere to move one if it gets bullied) or at least 125g for six. i keep 6 severums, 2 are in a 150g with 4 angels (who, in a 5 foot tank, still pick on each other occasionally) and the other 4 are in a 120 with some smaller cichlids and other fish. they used to be all together in the 120, but even when they were all under 3 inches, the tank was too small for them. there was constant fighting until i removed the dominant fish and the weakest fish. they were separated (from that tank and from each other) and then reintroduced in the 150g. now everyone is happy. while there is still chasing and they "make faces" at each other, there is no more physical contact.
and just as a side note, i don't like the writer's attitude at all. plenty of people keep oscars because of the behaviors mentioned in the article. discus and angelfish aren't wimps. my stupid angelfish used to beat the crap out of each other in their 55g tank, and it was never breeding-related behavior either. they're just mean. he wants to put geophagus in a tank with eggcrate on the bottom? great idea.... except that they simply shuffle the sand around and leave patches where the eggcrate shows through. i have one in my tank, and i have eggcrate holding down the silk plants. i would have to move the sand around everyday just to keep it looking nice.
