Is it possible to keep soft corals and lagoon corals without any powerheads or wavemakers except for a large airpump for flow? I will be using a lot of live rock but I want to try and create a 40G tank dominated by soft corals that is completely, or at least mostly biological. I do not want to use a skimmer, filter floss, or supplements. All I want to use is just the lights, airpump for water movement (a big airpump), heater, live 4" deep sandbed, 60 lbs. of very live rock, and soft corals with perhaps 2 or 3 small fish.

Is this feasible?

Your idea is interesting but the salt spray will be incredible.

gonna be hard because...
1) the bubbles made by the airpump will bring you water level down considerably everyday. and if your not careful your salinity could plummet.
2) it would be hard to get good flow to all corners of your tank with a lot of LR. even a BIG air pump would struggle to keep the water turn over good.
3) SW that is ejected into the air by the pump will most probably screw up your light.

i suggest just getting a power-head.
also i think your thinking that power-heads make the tank unnatural which is untrue because all they do is move water.

FTFY.

i was referring to if he topped off with RO water only.

You should have just pointed me to your thread instead of PMing me, dass.

Salinity would still go way up. Over time and with no compensation, the salt creep would lead to a gradual decrease in salinity, but that's over the longer term.

2 powerhead's and a medium air pump imo would be your best bet something like this to prevent salt creep onto lights etc





but closed on the left side too to make a half box at the water level these pics is my first attempt works good now that I redone it you can also do corner box too if you want

I only use the air pump for oxygen and to keep the water surface crystal clear and few powerhead's for circulation

only other problem you might run into is detritus build up a phosban reactor and biomax ceramic cylinder's will take care of detritus if you ever run into that problem

10% weekly/bi-weekly water changes will also help

My lfs has a filterless 40gal but they are running about 6 power heads on it. The key to a filterless aquarium is having plenty of flow. I'm not sure if your air pump would be enough, let alone the evaporation and (dare I say it?) micro bubbles. Filterless aquariums are fun though. If you have good live rock it should be no problem. Also, macro algae is extremely beneficial to such a setup...