I assume Lotus would do great in San Diego. Great climate for growing just about anything.

I don't think the water pH or alkalinity would have much if any effect, but the soil could. Like if you used potting soil that can be a problem depending on the type and quality. Regular backyard dirt should be OK.

Maybe more info would help. Like how is it dying, how deep is it planted, what kind of pot/soil, how/when do you fertilize, what do you mean your water is alkaline...that kind of stuff.

Hi
What type of lotus?? I grew them many years ago and the main problem was it overran the entire pool lol Started a tropical Asian type in Jan and until recently thought it was dying . Recently it has really begun to grow
Posted a pic on "shiroman lotus " in this forum .
They produce floating pads before the uprights. they are supposed to fade as it develops . Is this what you're seeing?? Is the tuber buried??
Was surprised that it took so long to grow though the tuber was completely dormant when I got it.
Seems to be headed in the right direction finally !!
Maybe you just need more time?? gary

My lotus used to have lots of leaves, both upright and floating. The upright leaves have decreased to only a couple and the floating leaves have decreased in number too. I bought it potted and it was wonderfully healthy. A couple of weeks after it was in the pond i had to treat the pond with a gallon of hydrogen peroxide to kill the string algae. That was over a month ago and the lotus is still dwindling. The surface of the pot is 3" below the surface of the water.

How large a pot?

The pot is probably a 3-gallon. It is big.

That's a good size for many kinds of lotus, a bit small for others and too small for the big kinds. Do you know what kind of lotus you have?

Lotus looks pretty in water garden but needs proper care.