Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Get the ferts more balanced. 1/8 tsp of each is not enough of some, too much of others, as shown by your water tests. It can reach the point that the excess of some blocks the plants ability to pick up the others, or else the plants use up all of the nutrients that they can get and need, but cannot use the excess of others.
Dose KNO3 until the NO3 ranges from a low of 5-10ppm to a high of about 20ppm. This might be at least double what you have been dosing. Try a week of at least 1/4 tsp, perhaps as much as 1/2 tsp.
Dose perhaps 1/2 as much KH2PO4 as you have been, or less. 1ppm is just fine. Lower is fine. Try 1/16 tsp or less for a week, see what happens to the PO4. Once things get balanced you might end up back at 1/8 tsp.
Whatever dose you find of KH2PO4 is right, dose the same amount of CSM+B or a bit less.
K2SO4 is optional if the KNO3 is enough.
Plants use a lot more potassium and nitrogen than they do of phosphorus.
Plants use even less of the trace minerals.
You cannot dose all the same. As you have found, the PO4 is not getting used, so it climbs, in spite of water changes. If you are using an iron test to determine trace dosing, aim for an iron test of .1ppm. This might not actually be enough Fe, but it is a reasonable way to measure the dose of all the other traces that are combined in CSM+B. You can add a bit more Fe in the form of a Chelated Iron. Try about 1/4 as much chelated iron added to whatever you end up dosing of CSM+B. For example, if you find out 1/8 tsp CSM+B is good, then add 1/32 tsp of chelated iron.
Adding more livestock does not directly raise nutrient levels. But when you add more critters you will be feeding them more. Fish and shrimp food are fertilizers, once they get broken down.
Fish food adds a fair amount of N, P and most traces. As you keep feeding more food you might find the N, P and CSM+B dosing can be reduced.
Fish food is low in K, Fe, and Ca and Mg. Ca and Mg come in with most tap water, but you might want to make sure, and see if you need to dose a GH booster (complete Ca and Mg) or else separate doses of Ca or Mg.
If you find the added food (for the added livestock) keeps the NO3 up, you can reduce the KNO3 and K2PO4, but you should add K2SO4 to maintain the potassium. I would add a chelated iron instead of too much traces. Traces can become toxic when too much are added, so just add the iron.
In a low tech tank, the fish food counts for more fertilizer and you just need to balance the dosing to supply the nutrients in low supply in fish food. In a high tech tank the plants use so much fertilizer that the fish food counts for very little.