Algae filter?

[eon aquatics]

Could algae be used in a DIY filter?
Such as a filter that moves water through a illuminated chamber with multiple panels that grow algae?
In contrast to bacteria bio media filters?

 

[Toby_H]

A refugium is when we use plants in our filter. While algae is not technically a plant, it could be used in the place of "plant" in a refugium.

Salt Water people tend to use far more complex filtration. I often go to their forums or How To's to get ideas. Though not all things translate equally. I believe they call what you are describing an Algae Scrubber.

 

[eon aquatics]

Does anyone here use these?

 

[Toby_H]

You can check out the next thread down from this one... https://www.monsterfishkeepers.com/forums/threads/freshwater-sump-refugium.763850/

I'm in the process of building a Sump that utilizes a refugium. I'll be using plants such as Pathos, Java Fern and HornWart. I won't be consciously targeting algae, but I expect it to be there.

Another poster, Triamond, is adding a lot of interesting details about nitrate consumption by plants. Google says algae eats nitrates faster than plants. Since both have the same basic needs, I'm very interested to see what comes of this thread too. I started the thread linked above. Feel free to derail that thread asking your own questions about algae as opposed to plants.

There's also a lot of information available out there already. With just a couple basic searches I saw several interesting pages/articles.

 

[Sassafras]

As Toby_H said, marine/reef keepers typically use algae filtration for nutrient export. DIY can be something like this where water sheet flows over a screen that is brightly lit by an appropriate color temperature lamp.


Algae is periodically harvested


Then there are high-end versions of algae reactors like this


Harvesting the algae

 

[duanes]

I have tried algae scrubbers, and found they work OK, but I have had the more success using higher aquatic, marginal and terrestrial plants.
My 125 gal sump/refugium below.


A dieffenbachia stem, above the main tank

And the water quality it helps produce.

 

[thiswasgone]

Could algae be used in a DIY filter?
Such as a filter that moves water through a illuminated chamber with multiple panels that grow algae?
In contrast to bacteria bio media filters?

In short, by itself no but as an addition to reduce nitrates and potentially prolonging the time between water changes yes. However, algae is not a unified tree of life and not all algae is beneficial. More specifically, algae scrubbers are effectively farms where you attempt to grow a specific strain of algae; typically some sort of hair algae within the chlorophyta division. There is a plethora of online forums and resources for you so I won't get into the details about how to set one up here but rather the pros and cons.

Pros:

• More time between water changes since most algae will suck up most excess nutrients including heavy metals such as copper.
• Great fertilizer for a garden or feed if you raise your own micro fauna (specifically "scuds"/amphipods)
• DIY can be very low cost for startup
• Scalable to any aquarium size

Cons:

• More electrical hardware to supply and maintain (lights) & potentially a separate pump depending on design.
• Scaling problem with space used vs cost efficiency
• Requires "harvesting" every 7-21 days
• Not a true replacement for mechanical filtration media
  • The main problem is the flow & by the time algae is thick enough to capture solids you should be considering when to harvest.
• Realistically not a replacement for biological filtration media
  • Could be a replacement but you would need a specialized room, not a container, dedicated to running angled lights & daily harvesting to maximize surface area for both beneficial bacteria (BB) and algae growth. Probably some sort of % split where you separate light to only some % of the bottom part of the media so the BB section won't have algae growth. This will also allow the water dripping down to carry nitrates directly to the algae population.
  • Not worth the $$$ and effort for anything less than a large pool/pond or extremely overstocked tank.
• Would compete for surface area with BB
  • Both BB and aglae are micro-organisms that, in theory, could actually live together in the same colony cluster but in the home aquarium our space is limited so typically it's better to maximize the amount of BB we can have compared to developing a self-contained ecosystem. Additionally, heterotrophic bacteria and other micro predators in our biological filters would eat any small amounts of algae that is present in the colonies unless you intentionally attempted to cultivate them -> a whole skew of new problems. In short, not worth trying to find balance in a single filter process.
• Extremely low chance to grow toxic algae species

It may seem like i'm bashing algae scrubbers a bit or perhaps bias but the things I listed are things you do have to consider if you want to make an algae scrubber your main source of filtration. Even as a supporting piece I would run the numbers to see if running your scrubber would be worth it or just continuing your normal water change cycle. Of course if you are using it as fertilizer, feed replacement, etc. then that may be different but usually for a freshwater tank I don't find running most algae scrubber setups worth it in the long run. Salt water folk tend to use them though since they pay the salt tax to run their tanks so dumping water willy nilly is a usually a no go.

My final suggestion is, depending on your stock, consider running a heavily planted tank instead of an algae scrubber similar to @duanes set up.