Wisteria Losing Leaves?

This is due to a lack of nutrients. Wisteria (Hygrophila difformis) is a very fast-growing plant, and that means more light and higher level of nutrients to balance. My attempts with this plant did the same, though in my case I believe it was specifically due to my very soft water as I was dosing a basic liquid fertilizer.

Substrate tabs willnot do much alone, as plants take up some nutrients primarily or solely via the leaves. A liquid fertilizer additive is better here, as the leaves and roots can take up the nutrients from the water.

What is the GH of your water? This matters as I mentioned above, because most liquid fertilizer preparations are geared for "most" areas that have moderately hard water. Those of us in areas of very soft water (my tap water GH is near zero at 0.5 dGH or 8 ppm) need to also add the "hard" minerals like calcium, magnesium, etc. which are present but not sufficiently in comprehensive liquid fertilizers.

To ensure I understand the lighting, you have four 48-inch tubes over this tank? I assume the tank is five feet in length? What are the tubes in Kelvin or CRI? It will say this, or might, at one end.

Byron.

My Wisteria also lasted for a couple months, can't remember exactly, but around 4-5 I think.

You willnot get this fixed without liquid fertilizer. Now, it needn't be the preparations like Flourish Comprehensive Supplement; you can also buy dry nutrients and mix your own. Those with high-tech setups do this as it is less expensive. I have low-tech so the liquid is not that much long-term when I buy the 2 litre jug which lasts me just over one year, used weekly in my six tanks. Don't know what tabs you were/are using, but they are generally more expensive long-term than the liquid, even if they were better or comparable.

As I said, substrate fertilizers will not provide all that is needed. These are excellent for targetting heavy root feeders like swords, aponogeton, lotus. But they are specifically made not to diffuse into the water column (to prevent possible algae issues) so the plants will not be getting everything. Now, water changes and fish foods also provide nutrients, but these may not be in sufficient quantity for the plants.

The GH you can ascertain from the municipal water supply folks, if on municipal water; they likely have a website with data posted, or they can ask you. No need to waste money on a kit and use it once.

Byron.