You'll have to decide up front what type of situation you want to have. Aggression would be least in an "all male" tank, since territoriality and confrontation is mostly associated with male/female pair formation and spawning. If you are planning to stock with young fish, and you are wanting pairs to form, you'd be best to obtain 4 to 6 of say, five different species and grow them up together in the 230G. There will be little interaction between these young fish other than competition for food. Once they hit around 4", you will notice them becoming more colorful and interactive, as they are reaching sexual maturity. Pairs will bond and territories will be staked out and defended. Once this stage is reached, it will be important to provide several distinct and separate areas, using rock, driftwood and artificial plants, that pairs can occupy and defend, and pursued fish can take shelter in. Larger plastic plants are useful to provide sight-line breaks and define these areas as well. It is at this time that you can start removing some of the extras. Adult Paraneetroplus can reach pretty large sizes (~12" for males and a couple of inches less for females) so it won't take many to fill the tank. I would say 5 or 6 adult pairs would be optimal for your 230G. Also, I find it useful to have a handful of younger, smaller cichlids in there as targets. They manage to keep out of harms way since Paraneetroplus are highly vegetarian and not the greatest at either wanting to eat or catching smaller fish. In one of my 180G, I have bifasciatus (3), fenestratus 'Catemaco' (2), "Coatzacoalcos (2), hartwegi (5) and a large bocourti. In another 165G, I have breidohri (2 plus several younger ones), regani (4), argentea (3), bulleri (2) and A. robertsoni Jutiapa (6). There are 7 or 8 other smaller fish in there too. This tank is a bit overcrowded but they all get along, believe it or not. Paraneetroplus are low to medium in aggression and rarely does an individual get injured. I have found that maculicauda are one of the more aggressive species, and might have to be watched a little more closely than the others, and breidohri are one of the most active, always on the move, challenging tank mates. Well that's just a few thoughts on the matter. I wouldn't worry too much about hybridization. It can certainly occur but I find that a healthy male and female of the same species will tend to pair rather than a mixed species
pair up. Having said that, I do have a male hartwegi that has spawned many times with a 'Coatzacoalcos female. I could explain at length why I think that happened but it would take too much time to tell it. It's a long story. And it isn't the norm. Good luck with your project. If I can be of any further assistance, please get in touch.
