Grass / Weeds growing between patio blocks

[Muggles]

I like them cold, but that's just me.

[Dan Espen]

I don't think salt is a good idea:

Soil Changes

A major problem with using rock salt even in small concentrations is that is tends to stay in the soil for years until water leaches it out. The salt raises soil salinity, which dehydrates the roots of plants and keeps them from absorbing necessary nutrients. If you add too much rock salt and it begins to affect plants you want to keep, as well as ones you want to kill, start watering the plants deeply every day to try to flush the salt out of the soil. You might not be able to save those plants, because it could take months of daily watering to return the soil to a viable salinity, but you can restore the soil so that new plants can grow.

Where to Use It

Salt doesn't always stay where it's put -- it can be washed off into your flower bed or lawn, killing large swaths of plants you want to keep. Some salt-tolerant plants such as the bigleaf hydrangea (Hydrangea macrophylla) can survive a bit of runoff, but not a full concentration of rock salt applied nearby. Apply the salt on a day with no chance of rain to let it soak in where you want it without the possibility of runoff. The best places to use rock salt are those where you don't ever want plants to grow, such as cracks in your driveway or along fence lines.

[Tony Hwang]

I used some kinda formulated sand to fill the gaps between paving stones. This looks like fine sand in white color. What it does it it settles very hard making it hard for the seeds to grow. I got it by the bags from local HD.

[TP]

replying to Moe DeLoughan, TP wrote: I have a uniblockPaver patio which is installed slightly below grade I get moss In the joint sand that was recommended most joints are a quarter of an inch or less in the spring when I power wash the moss out of these joints They just deteriorate at least large gaps in the pavers can you recommend a solution to thisThank you very much