I hope there will be time to respond in detail to this interesting article. But at present there is not. Therefore only a short commentary:
1. The most important thing seems to me that temperature is not the main problem for Parosphromenus-aquaristics. It may be for Discus (rather warm) or some Dario (rather cold) but I know of successfull breeding of Paros at different temperature-levels. I do not differentiate between keeeping and breeding. Breeding is the decisive test. Myself I have no heater in any of my small tanks. But the room temperature is in one case elevated to 23-24 degrees Celsius, in another to 2o-21. Good breeder friends artiiculate different experiences with temperature. The pioneer W. Foersch had no heater in all his tanks (varying 19-24 degrees Celsius), today the specialist M. Hallmann advocates higher temperatures (up to 27/28 degrees Celsius) than he did formerly. His argument is that such higher temperatures are measured at most locations in Indonesia and Malaysia presently. My opinion on this is that most present locations are more or less heavily disturbed, not natural any longer, with mostly missing rain-forest. Therefore, the influence of the sun is greater than at the unspoiled habitats.
2. Although the article is doubtlessly interesting and further discussion will be rewarding, it is (for our purposes) too general in my opinion. There are no thoughts on blackwater aquaristics and its specialities that make a difference to what 95% of the standard recommendations say. Nevertheless, the conclusion is similar. The author says: A stable temperature is non-natural; he is right. He says: Fish kept at lower temperatures live longer and are less prone to diseases; he is right if they are kept within their temperature tolerance – and this is bigger than often written and thought. But his conclusion “Keep fish at lower temperatures” is – to my opinion – wrong. It is too much generalized. And as Paros are concerned I should say more precisely: We have some problems (to care for a low germ level, to keep calcium out of the water, to maintain a rather stable pH, to feed them properly, avoiding Oodinium is a major problem, too) but temperature is not the problem with them. You can be successful at different levels.