[HeyPK]

Tell your friend that at least he should add some potassium to his tank. Fish food doesn't supply much potassium, and, with plants competing for potassium, fish can get into trouble. I know this is true for guppies. It may be that Discus can handle low K better, but guppies get whitish growths on their skin if the K gets too low. Adding K makes the growths go away after a few days and the guppies get more active and look better. If you don't add K when the fish get the growths, you will loose most of all of the guppies.

 

[HeyPK]

The LaMotte potassium kit is a good investment. It may seem expensive initially, but it has enough ingredients to last practically forever. You get a white cloudy suspension if potassium is present, and you can measure the amount by dipping a black dot into the suspension until the dot disappears in the suspension and then the distance of the dot from the surface is calibrated in ppm of K+. I never bother to lower the black dot thingy and measure the amount of K+. If I get cloudiness, then there is enough for the plants and the fish. If I don't get any or if I only get a very slight amount, then it is time to add more. When the guppies develop the white growths, there is no cloudiness at all. I only use the kit sporadically. it is when I think, Gee, I wonder if this tank has run out of potassium. It has been a long time since I put any in.

 

[HeyPK]

Phil, Let us know if your discus got better after you added the potassium. For my guppies, it takes two to three days before I see definite improvement in their activity and reduction of the white growths.