I love the idea of the living wall, it's going to look great! so you're going to use aquarium water to spray on the living wall? basically increasing plant mass? I wonder if that will throw off the fert stability in your tank with the terrestrial roots sucking things out. I would probably do a separate reservoir and just use a hydroponics premixed fert.
What type of plants are you thinking about? lighting?
It's a recirculating system, so water from the reservoir is pumped up to the top of the wall where 4 gph emitters drip it down to water the plants. The plan was to use aquarium water. The plan (as it so often does) has changed.
I went and talked with Steve at Aquarium Zen who has a pretty cool living wall of a similar design. His is pretty much just ficus pumila and spathiphyllum at this point. He said when the wall WAS recirculating but that plants just didn't grow that well-- the terrestrial plants wanted heavier fertilization, but it was negatively affecting the shrimp he was trying to breed in the tank that was acting as a reservoir. Nowadays he just sprays the wall down with a hose to water it, though he expressed interest in getting the recirculation going again. He also said I could probably get away with foliar fertilization, which does seem like a decent option.
Another factor is just my own personal desires-- I've worked hard to get as much tech out of the tank as possible, do I really want to stick a giant pump in there? It's not a big tank. It would severly hamper the types of aquascapes I could do. And when it comes down to it houseplants are really a secondary hobby to aquariums, I don't want to cripple one hobby for the benefit of the other. There are also other issues like potentially clogging emitters with fish waste.
So I ended up getting a little 7 gallon waste bin that will act as a reservoir with hydroponic nutrients. It will sit under the stand like a sump does. Plant list so far is:
Epriprenum aureum "Golden Pothos"
Epriprenum aureum "Snow Queen"
Epriprenum pinnatum "Cebu Blue"
Philodendron hederaceum "Micans"
Philodendron hederaceum "Lemon-Lime"
Philodendron hederaceum "Brasil"
Philodendron "Prince of Orange"
Philodendron "Mccolley's Finale"
Various phalaenopsis orchids
Scindapsus pictus "Silver Splash"
I'm expecting a good amount of attrition due to transition stress. I traded someone for a bunch of philodendrons and all of them were on death's door. I'm trying to nurse them back in some sphagnum moss but who knows whether they'll make it.
Lighting is just 6 feet of t-5 style LED grow lights that I'm hanging from the ceiling. All the plants can handle pretty low light so I'm not particularly concerned about that.