Aquaclear 30 Surface Skimmer

thingiverse

Remixed from "Surface skimmer for Aquaclear 20 HOB filter" Resized the cylinder to accurately slip fit onto my AC30 intake tube. Fixed the floor of the box to print the right number of layers at Cura's default 0.2 mm profile. At this time it still needs to be tuned for flow. It is definitely skimming the surface already! Two issues - 1) The water height of my aquarium must be lowered substantially to get this to work. I plan on printing a spacer for my AC30 to raise it up. 2) There are vortices forming off a few of the intake holes that are periodically connecting to the intake, causing the pump to suck a bit of air. I plan on tuning the depth of the box, along with the intake holes to get the flow right. Update - 10/1/20: I have optimized the design in several ways and also uploaded a spacer for the filter as promised. This spacer is for a 5 mm thick rimless tank. It raises the filter up 15 mm. The tolerance on the slip fit of the intake tube is critical. It is either a bit too tight or a big too loose. Erring on the side of too loose right now. Will test everything for a while and report back. Update - 10/5/20: After much research, many design iterations (https://imgur.com/lPgl3IT), and finally some math, I have decided to delete the teeth and go to a toothless design. The AC30 flows 150 GPH according to the documentation. The design was getting too large to flow enough with teeth in place. Thus, with the advice from the reef aquarium forums, I have gone with a toothless weir. Using the formula Q = 1.84(L – 0.2 H)(H^3/2) [https://www.cedengineering.com/userfiles/Sharp-Crested%20Weirs.pdf] I found that I needed about 100 mm of length if the head height is at 10 mm. If you don't have ATO, then as the water evaporates throughout the day the head height decreases and thus flow decreases until the intake sucks air. The operating range between an ideal thin surface skim and sucking air is surprisingly small. I set my water level to about 10 mm head height into the skimmer and I cannot go 12 hours without a top off before air starts getting in. I modified the spacer for the entire filter to sit 3 mm lower. You could also lower the skimmer on the intake tube or raise the water level in the aquarium to compensate, but it's a balancing act on my small ADA 45-F (<5 gal.), especially to keep aesthetics. Another option would be to increase the linear length of the weir to increase flow at a lower head height, but the box is already getting pretty big. Obviously an ATO will solve the head height problem completely. Feel free to remix the spacer and skimmer to fine tune the levels you need for your setup! Extra Note: Spacer was printed with 20% infill Zig Zag pattern to help with bridging. Update - 12/28/20: After running this for a few months I have some new thoughts. It's very hard to strike a balance that actually skims the surface without sucking air into the pump. When I think about it, this is not an ideal place for a surface skimmer, because the intake of the pump is directly inline after the surface skimming action. If you run the water level high you eliminate air into the pump, but you kill most surface skimming action. If you run the water level low you get some moderate surface skimming, but lots of air gets into the pump, it's loud and annoying and probably not healthy for the system. When I think about other surface skimmer designs they all dump into a sump. Therefore, you could run an extremely low water level for maximum surface skimming (and run a coast to coast overflow) and any air in from the drains quickly dissipates in the sump before clear water hits the intake of the return pump. Furthermore, the level in the display tank can be held at a more constant level due to the design difference between a HOB filter and a true sump setup. This makes this "surface skimmer" design moderately ineffective, but I will leave the design up for other people to try and maybe tinker with.