I am quite new to the marine hobby but have had tropical fish for some time.
the question is this

my water in my 5 foot tropical setup is excellent, all parameters spot on,
the parameters in my marine tank are also within specified levels
nitrite 0
nitrate 5ppm
ammonia nil
ph 8.2
phosphate .25mg

but I have a diatom problem as I have not yet invested in a ro unit, so
could I use mature water from my tropical to conduct water changes in my
marine having first adjusted the salinity and ph levels, and would this help
control my diatom problem. tia

Stuart