Hello, I have a couple of suggestions for a DIY algae reactor.
I would not try to run one of these without cooling the LED's. Those light strips you guys use don't offer much, so you are asking for excess heat, damage, maybe even safety. They are meant to be "stuck" to something, which gives them some degree of cooling even if it is not really heat conductive like metal. But wrapping them around provides none.
If you go with the "coaxial" design like the ARID, heat pipes are actually hard to make (but I have seen it done). Instead, you could use an off-the-shelf CPU water cooler (such as https://www.newegg.com/Product/Product.aspx?Item=N82E16835103236), and just run the water through the metal tube in the center. Then you just locate the radiator somewhere with good airflow, and/or put a fan on it. The only downside is you need a small circulation pump (that comes with it) so it is not a passive solution. But people in this hobby have lots of experience with pumps ;-)
IF you are going to go with wrapping the LED's around the outside way, here is an idea for that. Those LED's already come with an adhesive backing, all you need to do is stick some of these tiny heatsinks behind the LEDs: http://koolance.com/video-ram-heat-sinks. These are also self adhesive, but you can get one's that are not, and some of them even use thermal adhesive pads that conduct heat better.
This does not solve all the problems, but I wanted to share this for the cooling issue.
-JCL
Just wanted to be clear... I do not own an ARID reactor. I just talked to the owner on YouTube and he gave some helpful advice, such as reflective surfaces for the light to bounce back, ect...
The algae we're using is an underwater species of macro algae plant, thus the submersion of the algae. You were suggesting to grow it like a hydroponic setup, correct? Micro algae can grow like that via a turf scrubber, but also adheres to the surface. Chaetomorpha algae, which is what is used in these reactors, doesn't grow onto a surface like micro algae does. It's just spaghetti algae in a ball and makes a huge mess when you have to trim it. The reactor helps contain that mess as well. Not to mention if you hypothetically put an air stone in front of the reactors pump, and even if it doesn't damage the pump, you'll probably make the pump much louder at night, and also have the efluent releasing near your return pump which would send bubbles into your tank, unless you release it back to the beginning of the sump. Honestly, no one has done something like that and I couldn't tell you either way if it would provide a benefit in a reactor setting. It almost sounds like putting macro algae in a protein skimmer with lights. But skimmers use much better pumps than the cheap type used for an algae reactor. I also couldn't say whether or not chaeto and air bubbles agree with each other. But someone can always try it out, but you'll probably have a build up of air in the reactor that doesn't escape. Remember, they're not open like a skimmer.
Also having an abundance of CO2 in the tank is a real issue, even with a skimmer running. If your ambient air is CO2 rich, because you have a lot of pets and/or people breathing in the area or a closed off house in the summer with the AC running, then a skimmer is just not going to cut it. Surface water agitation is where your gas exchange happens, and with a CO2 dominant enviornment, you're possibly adding more CO2 than oxygen, depending on your surroundings.
We've moved past wrapping the lights directly onto the reactor because of the heat issue. What some have done is have a big piece of PVC pipe and wrap the inside of the pipe with the led's, then put it over the reactor so there is no direct contact with the reactor. Just passive air flow seems to be enough. A clip on fan at the worst case would be needed.
Another member a few posts up explains that they attached the LEDs to an aluminum housing to use as a heat sink and for its reflective properties, but found it didn't disperse the heat in a way they thought.
You will always have to have a pump to move the water through the reactor with some sort of flow control. You either use a low gph pump or take one you already have and use a ball valve to control the flow through it. The size of the reactor isn't so much sized on the tank, it's more sized on your bio-load and if you have a lot of nitrates and phosphates for the algae to thrive.
Running the reactor on a reverse photo period from the tank provides benefits to both the tank inhabitants and the algae. It will provide a natural way to oxygenate the water at night when everything else is producing CO2, and therefore giving the algae an abundance of CO2 during it's lighting period. This also reduces or stops the Ph swing at night.
So you can have a huge tank with a big reactor, but if there aren't enough nutrients to support the algae to fill the reactor, then you have a bigger reactor than you need and algae will start to die off. Basically if you have algae growing in your display tank, this type of reactor will eventually out compete it, depriving it of nutrients. There are a few different algaes with high nutrient uptake and that is why Chaetomorpha is used (plus it will not adhere to the surfaces of the reactor).
However, if you have a constant flow of nutrients, a bigger reactor would be more appropriate. The algae will keep growing and you'll have to harvest it less often.
The main issue has been finding led's that are consistent and cheap enough. Some don't have the proper resistors and the blue color will burn out, some don't have the proper setup as far as power and are dimmer towards the end, some run very hot, and these issues can all be from the same brand of led's. It's a crap shoot to what you'll get. Others seem to be so expensive that buying a ready made reactor would be more feasible.
And keep in mind that anything you run the water through has to be aquarium safe in that it won't contaminate the water in the tank.