The Puffer Forum

I'm not neglecting the plants, I just know for sure they don't help much with stunting. Nitrate stress, yes, stunting no. Plants don't absorb fish hormones and other subtle outputs, and in general don't improve water quality fast enough to allow really heavy overstocking. Unless you've upgraded the stock light a lot, the dwarf hairgrass is unlikely to make it, the stuff likes REALLY high light and is as far from the bulb as you can get in a tall hex. The 2.5 gallon I had was at over 4wpg with constant heavy plant growth, it didn't matter enough and the fish was stunted, and that was one DP in 2.5 gallons. Lets say I had only 2 gallons of actual water, and you have only about 4, due to substrate etc - you have twice the space I did, and 12 fish other than the DP. I can only conclude most likely your DP will be stunted no matter what you do, as well as the other fish, unless they're already adults, in which case their lives will simply be shortened. You aren't a little overstocked into the reasonable with high maintenance area, you're way way overstocked. Five times times the fish your tank can hold isn't a good idea, even with the 50% daily water changes I suggest it's a bad move. I also said in my post that by crowding cichlids, I meant actually going with ALMOST an inch per gallon despite their size, you're more overstocked than that, and your fish are not resilient cichlids, they're a combo of sensitive tropical fish and relatively hearty(but still not like a tough strain of cichlid) white cloud minnows. If you were trying to keep nothing extra but 4 or so white clouds with the DP in the 5, there might be some wiggle room with lots and lots of plants, high lighting, and massive water changes, but I think you're well out of the range for it being advisable with any level of maintenance. Think about it this way, your tank is the equivalent of a dozen people staying together in a small studio apartment where nobody can get out. Sure plants will improve the air quality, really good ventillation will improve the air quality, but it's still 12 people in a 150 square foot space, and none of them are going to be happy about it.

Ok Nick, I undertand your point of view, and appreciate your replies because I did after all join this forum to discuss, but I would really like to do some more research on stunting before discussing that issue further. The issue of fish hormones is interesting to me and I would like to read up about it. When it comes to schooling fish however, I do not equate the tank with a small studio. I see my tank as a small ecosystem, one that I maintain a lot of life in, and the point of this exercise was to see whether I could curb a single dp's aggressive tendencies towards other species by providing a stimulating environment.
I'll get back to you guys in a bit.

Hormones are one of the suspected factors in fish stunting, since nitrates alone don't tell the whole story; tanks with good denitrificaiton can still stunt fish, and hormones and other subtle dissolved organics are the most likely culprits. The actual material size of the tank isn't going to actually matter, as the fish has now way of biologically knowing that without something concentrating in the water which it's systems can respond to. A hex tank is a good choice from a crowding to dissipate aggression angle, as it creates very little territory. An experiment was done with ten or so grown oscars in a 75 gallon tank, with nearly 100% daily changes(tank taken down till all the fish were laying flat on their sides in a puddle), and seemed to work acceptably well, but 100% changes removes ALL organics and totally alters the nature of the game. If you were going to try that, your stocking might work, but it would be quite stressful to the fish you have, so perhaps 85% daily would be a good compromise, so as not to beach them, they aren't as tough as oscars. Thank you for being able to listen that my experience indicates what you are trying is not going to work out long term without taking it personally. I think that if I were trying your experiment, I would use a group of 6 of these:
http://www.gsas.org/Articles/1998/het-formosa.html instead of the fish you have.
They often don't grow past a half inch or 3/4", so the bioload would be minimal, but there would be plenty of activity to distract the DP.

Thanks for the suggestion! I also considered some Endlers.
Just to let you know, I'm stepping up the water changes. It's not exactly a lot of work, just the small water changes more frequently were recommended by members of another forum so as not to drastically change the water chemistry and shock the fish, so I went with their advice, but I don't think it will hurt to do more than 15%.
A good thing however is that I've not yet seen any adverse effects commonly seen in stressed out fish such as suceptibility to disease, faded colouring or bizarre behaviour, and in fact, I think the glowlights might be trying to spawn? Not sure, but will find out eventually.