Using Seaweed to get rid of nuisance algae in your aquarium or pond

Discussion in 'General Reef Topics' started by SantaMonica, Aug 1, 2016.

to remove this notice and enjoy 3reef content with less ads. 3reef membership is free.

  1. SantaMonica

    SantaMonica Fire Shrimp

    Joined:
    Jun 15, 2008
    Messages:
    306
    Location:
    Santa Monica, CA, USA
    Using Seaweed to get rid of nuisance algae in your aquarium or pond, part 1

    One of the neat things about nature is that it's had a long time to figure things out. Especially under water. Here, nature has figured out how to reduce all the "nutrients" to very low values, and also how to feed every aquatic animal (as well as consume half the world's CO2, and produce half the world's oxygen), by just using sunlight. Not bad. Maybe this concept can be used to help your water pets.

    Well of course it can. And it is already doing so, sort of. It's just not being used enough, or even on purpose. It's sort of the difference between a bicycle and a motorcycle, or a snack and a big dinner. Or even knowing you have a dinner in the first place. It's called photosynthesis.

    You have all heard about photosynthesis; it reminds you of trees and science experiments. But how can it help? Well the basics are this: Photosynthesis takes carbon out of carbon dioxide, and uses it to build living things, and it releases oxygen in the process. You've probably also heard that all living things contain carbon; well, that's where the carbon comes from, and photosynthesis is how it got there. The living things that photosynthesis builds generally are plants (on land) and algae (seaweed and phytoplankton) in the water. Then, anything (like you) that eats these plants or seaweeds will get the carbon you need to grow. Oops, there is one more neat thing that photosynthesis does when building these living things: It uses Ammonia, Nitrite, Nitrate, Phosphate, and many metals like Copper and Iron too.

    Sounds like an ideal filter, right? Removes Ammonia, Nitrite, Nitrate, Phosphate, CO2 and metals, and put oxygen into the water. Also sounds like an ecosystem, like the ocean, or lakes, or rivers. Because it is! That's how the oceans, lakes and rivers are naturally filtered!

    So we will be showing you how to build your own DIY versions of these neat filters (for fresh or salt) in the coming posts.
     
  2. Click Here!

  3. SantaMonica

    SantaMonica Fire Shrimp

    Joined:
    Jun 15, 2008
    Messages:
    306
    Location:
    Santa Monica, CA, USA
    Using Seaweed to get rid of nuisance algae in your aquarium or pond, part 2

    So how does photosynthesis "pull" the carbon it needs out of the air or water? Doesn't CO2 or other nutrients just "soak" into things by themselves? For example, doesn't CO2 just soak into trees? Meaning, if you have more trees, won't more CO2 just soak into them? No, not really.

    CO2 and other things do "soak" into water, but the reason that the water does not "fill up" with CO2 is because organisms in the water "pull" and "eat" the CO2. What organisms might these be? Algae, of course. Or more specifically Photo-Auto-Trophs (photoautotrophs), which means they get their food (carbon) all by themselves (auto), without needing to eat other animals, and they do this using sunlight (photo). In the open ocean and open lakes, all this is done by free-floating algae (phyto plankton), but as you the get to shallower areas of the reefs and lake shores (and in streams and shallow rivers), it is done by benthic (attached) algae on the bottom surfaces. We will be calling all attached algae "seaweed", even if it's in freshwater lakes, because saying "lakeweed" is a bit odd.

    The faster that carbon is taken out of the water by the seaweed on the bottom surfaces, the faster CO2 can continue to absorb into the water at the water's surface. This is an important idea to understand; it forms a CO2 "gradient". This idea is easier to explain by thinking about an oven: Standing far away from an oven, you might barely feel the heat, but as you move closer to the oven, your temperature rises. So even though the oven is making the same heat, the amount of heat you feel depends on how close you are to it.

    With seaweed on the bottom of the reef or lake, the amount of CO2/carbon the seaweed "feels" depends on (among other things) how close the seaweed is to the surface of the water where the air is, because this is where CO2 is being absorbed into the water from the air. This is one of the reasons (besides light) why all the phytoplankton lives near the surface of the water. Seaweed however is far from the water surface, and water that is next to the seaweed (say, 1 cm away) has had so much carbon removed that there might be little carbon remaining. So by making the air more near to the seaweed, it feels and has access to more CO2/carbon. This "near-ness" of air to the seaweed is what makes things work for our filtering needs.
     
  4. SantaMonica

    SantaMonica Fire Shrimp

    Joined:
    Jun 15, 2008
    Messages:
    306
    Location:
    Santa Monica, CA, USA
    Using Seaweed to get rid of nuisance algae in your aquarium or pond, part 3

    Thinking back now to the oven, and to the heat concentrated inside it, it becomes clear that if that same heat were let out of the oven, your house temperature would get hot, but not near as hot as the oven was. Why? Because the oven concentrated the heat into a small area. And, if you let that same heat outside your house, it would not warm up the outside air at all, for the same reason. If someone did open up all the windows and doors and let the heat out, you would need to stand right next to the oven to get any heat at all. So even though the same process and amount of heat exists, the area that you concentrate it in makes the difference. So going back to photosynthesis, which is the filter we want to use, the amount of filtering it does is based on the concentration of certain things:

    The first is chlorophyll. This is the filtering engine that pulls the nutrients out of the water, and the more of it there is (higher concentration of algae), the more nutrient can be pulled out per hour. The second thing needed in concentration (and to keep the chlorophyll alive) is:

    Light. Any part of the algae that has reduced light cannot pull nutrients out as fast. This is only up to a point however: If the light gets too strong, then the photosynthesis completely stops and the algae die. So the trick is to keep a strong, even, constant level of light concentrated on all the algae at all times, with the exception of the "off" time for the algae to rest. And let's not forget about the concentration of what we want to filter:

    Nutrients. This is like the heat in the house. If you keep the windows and doors shut, you will feel more heat. But if they are open, especially if cold wind is blowing through the house, you will need to be right on top of the oven to warm up. Algae, too, need to "feel" and be near the nutrients, which are stronger near air/water interfaces that supply more CO2.

    Once you are warmed up by the oven, it's time to let the next person stand next to it. Then the next, etc. You can even go into high rotation of letting many new "cold" people stand by the oven for a brief instant, while the others move through the room waiting for their turn. This is how nutrients are supplied in high amounts to the algae; a new group of air/water interfaces is brought in every second, so that the algae see and feel a high concentration of nutrients right next to them, even though a few millimeters away the nutrients are low.

    So let's see how we can build such a filter that let's us concentrate these things.
     
  5. SantaMonica

    SantaMonica Fire Shrimp

    Joined:
    Jun 15, 2008
    Messages:
    306
    Location:
    Santa Monica, CA, USA
    Using Seaweed to get rid of nuisance algae in your aquarium or pond, part 4

    Let's start building our filter with the understanding of what the algae need to pull nutrients out of the water quickly: Light x Attachment x Turbulence. The light is obvious, and the attachment keeps the algae in place so the turbulence can occur without washing away the algae. The turbulence is the part mostly people don't understand, because they see algae in their tank without much turbulence. What they don't see is the rate of nutrient absorption; it would be very slow without turbulence, sort of like you standing in front of the oven and not letting other people get their turn to warm up.

    Lighting is the simple one: Photosynthesis likes red and blue color light. It absorbs red and blue, and uses it, but it does not use much green. So green is reflected back to you, and that's why lots of plants and algae look green. And for algae, it turns out that mostly red is needed. Matter of fact you can use only red if you want to. 660 nm (nanometers) in particular, which is called "deep red". 630 nm works too. And you can add a little blue, such as 430 nm if you want, but the red does most of the work. "Plant grow" lights can be bought which already have these colors.

    Three main types of attachment material exist: Rocks, strings and screens. Algae have developed a natural enzyme to allow them to bore into solid rock and attach to it, so if you use rock (live rock, or silica rock, for example), then the algae already know what to do. Strings, and screens, which are "new and unfamiliar material" to algae, work by offering the algae places to wrap around and attach back to themself. So while algae may not dissolve holes into nylon string or plastic screen, an algal strand can do a wrap-around and attach back to itself. Once it does this, it's as solid of a grip as with rock.

    Turbulence, as in a thin air/water turbulent layer, is the area where all the work goes into when building, and decisions have to be made how and where you are going to be filtering. You want a lot of turbulent "turnover" touching the algae so that new nutrients are brought to the algae each instant, and you want a very thin layer of water separating the algae from the air, so that what's called the "boundary layer" of water surrounding the algae will be very thin, thus allowing CO2 and nutrients to get in and out of the algae easily. It's like giving everyone a turn to stand in front of the oven to get warm.

    There are three basic ways to provide this air/water turbulence: Rivers, waterfalls, and upflows. A fast flowing river does provide fast water, but the air/water layer is rather thick because the river can get deep easy. More than about a centimeter deep will almost halt any rapid algae growth. Also, light can only reach the growth from the top, so rivers are essentially only 1-sided, which means that the bottom of the river, under the most growth, gets dark easily and can die; this stops your filtering. Therefore since rivers are less efficient, they need to be bigger to give an acceptable amount of filtering.

    Waterfalls solve both of the problems of rivers: The air/water layer stays thin, usually 5 mm, and if the waterfall is flowing down a thin screen with a light on both sides, then the waterfall is 2-sided instead of 1-sided. This light on both sides keeps the "roots" of the algae alive longer, so it holds on longer, thus letting it grow and filter more. Waterfalls must be above the water however, so they take a lot of space. And if the water stops, the growth dries out.

    Upflows, using air bubbles under water, improves upon the air/water turbulent interface of waterfalls because when air bubbles rub the algae, essentially the thickness of the water at that spot is zero for a brief instant. Plus there is an in-and-out swishing of the algae as the bubbles go by. This motion provides the thinnest boundary layer around the algae, and thus offers the least resistance to nutrient and CO2 flow into the algae. Also, upflow cannot dry out, because even if all bubbles stop, the algae just stay under water. And of course, being already under water, they essentially take up no extra space.

    So next time we will start making some things.
     
  6. Bluelobstor

    Bluelobstor Plankton

    Joined:
    Jan 2, 2017
    Messages:
    2
    Thanks for the info so far and I will be following this thread.