This is my test pothos. I completely neglected it for one year with LECA as substrate for semi-hydro in a small 1,5 l pot.

All my other established (house-)plants get "flushed" once every few months, around once a quarter. I basically just discard the few hundred millilitres of nutrient solution and refill the pot again from the top.

Some people say you need to

• Really flush it. Run the shower through it or whatever, and
• Do that once every two weeks.

I call that total BS, at least in my experience and with my conditions.
I only do this on new plants where old soil roots and dirt are rotting and need to get out.

I took EC and pH measurements from time to time, and never saw much changing. No increase in EC (incoming nutrient burn), nor decrease (incoming deficiencies), nor pH changes.

I use Masterblend as fertilizer, with the recommended concentration for blooming stage, and reverse osmosis filtered or rain water.

The top layer of the LECA is pretty much always dry, and I didn't see much of a fertilizer crust because of this.

I also gifted a Calathea-type plant (sensitive to minerals) to a family member. She uses a long term fertiliser and tap water most of the time. There is a mineral crust on top, but the plant looks okay. She also rarely flushes. Works fine too.

When I repotted today, everything looked fine on said pothos.

All of this tells me S/H seems to be even less work than people say, which means a lot, because it already is super low maintenance!

Still, one of the big pros of LECA is that you can flush it, and you definitely should from time to time.

If you use a high quality fertiliser (one that also includes trace elements and Mg/Ca) you probably don't need to expect much nutrient issues if you use RO water.

If you use tap water then flush it a bit more often to prevent nutrient lockout due to limestone buildup.

But there's a lot of disgusting stuff building up over time, like plant exudates or dead roots.

I will continue to flush only from time to time, because it keeps everything hygienic and fresh.