This is my first planted tank in over ten years. I used to keep planted tanks with just city water, maybe a little DIY CO2, and fluorescent tubes, and had pretty decent success.
Then I had SPS reef tanks for about a decade. They did really well and I am pretty stubbornly set in the mindset of "start with RO/DI, add what you need, and test for everything that you add, and for goodness gracious, do NOT add anything that you cannot test".
It does not seem that the way I kept sps tanks is the way people keep planted tanks, because I am not having any luck finding guidance on what specific parameters I need to keep my water at. It's driving me crazy!
I see a lot of recommendations to just use tap water and that a wide range of parameters is OK, but my rural well water is off the charts hard and high pH and Alkaline. I would like to keep tetras and other soft water fish, and this just does not seem like a good idea to me to use that well water.
I could use the water from my house water softener, it reads more neutral in most respects, but I really worry about the salt from the water softener being bad for the plants. (Is this much of a worry?)
So what I am left with is RO. I have been using RO water from my small unit for making drinking water, and adding a very small amount of my unsoftened well water to add back in a little bit of minerals.
This gives me tank water with GH and KH of about 4, pH about 7.2. Tank water reads Nitrates about 20-30 ppm. I don't recall the other values off the top of my head (I am at work now).
I have read about EI dosing, and right now I am resistant to it because I make up the water with my small RO unit, and while I can occasionally do a 50% change, coming up with 50% of my tanks volume every week is going to be a pain in the butt logistically. Although I suppose I could just pick some up at the fish store.
There is something wrong with my tank. The leaves on my sword plants are thin and seem to develop holes. Most of the plants grow slow. Also, the fish are not thriving. My cory cats slowly developed eroded barbels over several months, and then died. My black neons seemed so robust for a while, and then just started to look bad and one by one, almost seemed to get sick and die.
I believe there is a water quality issue, but I am not sure where to start in diagnosing it. And, I am not sure if the fish not doing well is related to the plants not doing well, or what.
What I would really like to know, is what are the water perimeters I need to monitor to keep healthy fish and plants (including fertilizers) and what are the optimum values for them.
Unless there is another way I need to be going with this? After reading my rambling tale, does anyone have any thoughts on this? I am really stupefied as to what is wrong so am open to any guidance.
Additional details: Tank is 40 gallon, lit by a single 150 W MH/HQI bulb which is on for 9 hours, and I run DIY CO2. Been running for a little over 6 months. I use root tabs but that is the only Fert. Since all my tetras and corydoras died, the only fish I have are a single pearl grouami and a pleco. I am scared to add more fish since I don't know why the others failed to thrive.