New to water
I have the nagging suspicion that one of my water parameters are off. I have a master test kit (pH, ammonia, nitrate, nitrite) but I've heard people discussing other variables that I'm not familiar with. Can someone point me in the right direction in what to buy and what to test?
I have a 50 gallon tank with undergravel filters attached to powerheads (that have sponges over their intakes). There is also a filter that uses a powerhead to push water through a water bottle packed with the dense roots of a pothos plant (powerhead also has sponge). I use it to keep my shrimp (part of the reason I think my water parameters are off) and it is somewhat heavily planted. It is well-lit with 4 27 watt CFL bulbs and one LED bulb. There's a piece of malaysian driftwood in there and currently one indian almond leaf. There are lots of ramhorn snails. The plants are so dense that I rarely see any of the shrimp. I originally bought 30, but I think that number is down to about 10-15. I saw some confirmed deaths when I was making rookie mistakes with the tank (overfeeding, filter accidents). Though if they died, I really wouldn't know if it even happened or not (ramshorns and other shrimp probably got to them first). The original shrimps I bought (dunno who's still alive) were 10 dream blue velvets, 10 dream blue X blue velvet culls, and 10 cheap blue velvets. I haven't seen the dream blues for months (finally saw one about a week ago. At least I know one is alive...) The pH stays at 7.4. Nitrate, nitrite, and ammonia all generally stay at 0 ppm, although the nitrate went up to 20 ppm recently. I do weekly/bi-weekly partial water changes. The temperature hovers around 74 degrees F.
A couple things have made me suspect my water is off
-Certain plants have grown well (Vallisneria Contortion Asiatica, hornwort, elodea), but others that are known to multiply quickly have remained stagnant (java fern, glossostigma, dwarf grass, brazilian pennywort, Dwarf Sagittaria Subulata). I'm wondering if a couple minerals are off, preventing them from growing. I realize CO2 might be the remedy, but I don't think I'm wiling to risk my shrimp with that.
-The shrimp aren't thriving. They hide all day. The only ones I regularly see are the cheap blue velvets, which I'm assuming is because they're more vigorous than their inbred cousins (the beautiful dream blues). I'm wondering if I should get a mineral block or something.
Thank you guys in advance for your valuable feedback!