Some thoughts on my setup as I reflect.
Looking back 6 months...
A typical off the shelf hydroponic tray is a viable alternative to a traditional tank. I've now used the botanicare 42"x24"x7" tray for 6 months as a frag tank. This tray had been previously used to grow plants and enjoyed nothing more than a simple scrubbing with a scotchbrite pad to clean her up. I drilled a hole near the waterline for the 1/2" return bulkhead, and installed a 3/4" bulkhead and standpipe in the natural drain location of the tray. Circulation consists of a Panworld 40PX external pump as the return, with a single Tunze 6100 stream pump located in a corner. When full the tray bows out about 1/4" at the middle point. I initially complained about detritus but it turns out it wasn't so bad. I think it's a cheap and effective method for growing small frags, and other corals where horizontal distribution exceeds vertical (tables, plates, and clams). i assume it would work great for zoos and xenia and stuff like that too.
I placed a single 250W MH about 10" above the water surface in a spiderlight reflector. I started with an old (but new) 6500K Iwasaki I had lying around then switched over to a 20K XM. The tray is white so I get tons of light bouncing around inside. With the 6500K bulb I had to wear sunglasses to look into the tank. With the XM I don't feel as if I need to, but it's still pretty bright so not a bad idea. I built a few screens out of PVC pipe and various materials to attenuate the light for new additions, etc.
Heaters are a 250W and 300W submersible heater controlled first by themselves then by a Watlow controller with DIN-A-MITE SCRs. I've played around with Watlow stuff extensively in my "day job" and it works very well. Set it to 77 and forget. I do not have an overtemp problem yet and not sure if I will this summer (or fall) or not.
I've been using IO with homemade 2-part tweaks for Ca and Mg. Initially changed about 20gal/wk, now down a little to 20gal/2wks. 20 gallons is the size of the mixing container.
Topoff started as dilute 1 gallon kalk drips refilled every day. I'm still relying on dilute kalk for making up a little over 4 liters of evaporation a day, but I've been using a peripump to pull from a 5 gallon resevoir. Every few days I manually open a valve to refill the jug.
I feed a few drops of OF and RF 2x daily, and a few drops of PF once in a while. Things are growing more than dying!
Controller is industrial - a NI PAC (cRIO w/FPGA). My IDE is LabVIEW. Sky's the limit with that baby. She's hooked up into my home network and although the controller runs headless, I have a little app that I use for control and monitoring when I want. I just FTP off CSV log files currently set to 1 second resolution (OK I'm guilty of oversampling but I don't have a storage problem.) I create a new file every 8hrs to keep within EXCEL limits. Is it still 32767 rows??
I'm farming on a mix of a few BAF plugs on eggcrate, some stuff glued to the bottom, and a GM-clone acrylic tray. One super useful thing was to tap the corner holes of that tray and install M6 nylon screws so I can adjust the height of the tray.
And one thing I've been religious about dipping everything on entry and each piece again after 3 days. I don't have any mainstream pests that I yet know of. My lone fish spent 6wks in the q tank/slammer. I wrote ACCLIMATE on the side of the tank as a reminder.
Moving forward 6 months...
Integrate the rest of the process equipment. More on that later, might just start another thread for that topic alone since I know some of you like it. I've been garage R&Ding a fair amount last 2 weeks and have some new stuff coming online.
Build a dedicated PDU and put the electronics and a surplus touchscreen into it. I reckon it will be pretty sick when it's all done.
Ca Rx? Yeah "perhaps in the next 6 months."
Back to weekly but smaller water changes.
And when the stuff gets bigger move to a deeper tank. I really only have about 6" of water, which is not a limitation yet, but it will become one.
Raise the MH another 4 inches. It's too close. That or downsize. That actually is priority #1.
Increase flow through sump. Not from tank but inter-sump circulation. It is way too big for the tray, and the flow in my return chamber isn't enough to break up the surface scum that collects. It's not even high enough to avoid a little layer in the skimmer chamber - I feed directly into that chamber via a bubble tower. This baby is sized for my twin 80's not my measly 25 gallons or whatever in the tray.
Generator.
Work out plan for over temperature.
Stop supergluing my fingers together