First topic:
Nutrition control. I.e., nitrate & phosphate.
long version:
To me, there seems to be only a few general category of nitrate control. The few that I can think of are: water change, protein skimmer (with and without bio pellet reactor) & algae (macro & algae turf scrubber). Water change is not a very effective way to maintain nitrate. It can be used in an emergency but removing 10% water per week is usually not sufficient. For example, suppose your nitrate input is approximately 2.5 ppm per week. Then your equilibrium per week will be around 22.5 ppm - 25 ppm. The second method is with a protein skimmer (with or without bio pellet) which I admit I do not have much experience with. This is the most popular method for most aquarist and probably the most reliable for larger systems. The issue that I have with it in regards to the Ugly Box is that it takes up A LOT of space or some external pumping to a sump which I would like to avoid. The third method is using macro algae or algae turf scrubber. One method is to simply have macro algae in the frag tank and since the tank will not have any macro algae eater, it will not succumbs to predation. Algae turf scrubber (ATS) is the method that I have been using for my 55 gallon tank and it seems to work decently well. It also has it's issue with fairly annoying process to maintain/clean. Fortunately, it's one of those once a week deal. Currently, there seems to be 3 main design for ATS which are vertical waterfall, horizontal & upflow. Waterfall involves pumping water to a standing pipe and allowing it to vertically fall down a screen of algae. This is the most efficient method but takes up just as much space (if not more) then a protein skimmer. The second method to pump water over a horizontal screen of algae which is also very space consuming. The upflow method uses an airstone which creates an upward current in an enclosed space. This method is compact but I do not know how efficient it is for low nitrate systems. For what I have in mind, see tl;dr version.
For phosphate control, I only know of 2 methods which are GFO reactor & algae (macro & algae turf scrubber). GFO is automatically not viable due to the pumping constrains which leaves us with algae. Since both idea situation uses algae, I think it algae is probably the ideal solution for the Ugly Box.
tl;dr version:
There is no reason why we should be deathly afraid of algae (especially in a frag tank). In fact, the right type of algae can be very beneficial in removing nitrate and phosphate while still leaving trace amount in the water column for coral to use. The main issue with algae IMO is that it gets all over the place. It will grow anywhere that it can attach itself to which includes the frag plugs. Macro algae such as chaeto do not have this issue but I doubt it's ability to compete with hair algae, etc. to completely eliminate it. So the issue is how to grow algae while isolating it to a specific location for easy removal. One method is using algae turf scrubber (ATS) but since the Ugly Box does not have aesthetics constrains, I think we can rethink how to design the ATS. Essentially, the sides of the frag tank receives a considerable amount of wasted light. If we create a screen on the sides of the tank that allows algae to grow on, we can reuse this space and light as a method to remove nutrients. Additionally, there should already be sufficient flow in the frag tank so an extra pump is not needed. One potential issue is that algae also goes through day and night cycles which means that dissolved oxygen might drop significantly at night.
Let me know what you think of the design so far or if I should take a completely different route. If you also run frag tanks, I would like to hear how you are doing with nutrients and your removal method.
. I always thought that you need a reactor for GFO since the material is soft so you don't want it to physically hit something or high flow going through the material. Thanks for the info. I will probably have to rethink GFO.