I was wondering what the best strategy for keeping ok planets that I just invaded from being taken back again.

The best would probably be to brick, have my legion defend it, boost it with temp artis and Planet vortex deflector and use a hard flux.

My issue is what to do with planets that don't warrant the use of a hard flux, I got several 15x mining planets and a lot of arti planets producing 150- 200 (p/H) planets that I would like to invade the issue is how to keep them. A lot of these planets are owned by lvl 1000-1500 players.

So far my best idea is to invade, extract anything nice, brick, guard and soft flux after a week. This does however mean that I need to produce a lot of Temporal fluxes orbs.

This

for a lot of the maxed toxics and 200 ph arti planets held by rank 1200+ players they wont bother taking them back - purifiers are really common and they can make up the arti easily, and their invasion costs are sky high. So I wouldn't worry too much, although if they are nice, soft flux them.

For most terra planets that can produce 250+ ap I invade, throw something like 15k pop on, vortex and guard it. The energy to drop the pop to the point they can kill the guards is so much that its enough to put most people off. You can soft flux it after a while and then either pp it or keep it defended

Of course, they'll often be alerted for rank 600- players who can really use them, so the soft flux is definitely a good idea.