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Beat the Bloom: Practical Algae Control for Hydroponic Reservoirs · Hydroponics Daily

• 0:00
  Hello there and welcome back to
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  Hydroponics Daily, your go-to podcast for everything soilless cultivation.
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  I'm Dr. Russell Sharp, the owner of Utrema Limited. We make a number of specialist
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  inputs for hydroponics, including but not limited to gold leaf in the US or
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  liquid gold as it's called here in the UK.
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  Today we're diving into a green problem and not the kind you want.
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  We're talking about algae growing in your hydroponic or your glasshouse reservoir or tank.
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  Now we've talked in the past about cleaning and sterilizing your tank and we
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  talked about those two different things.
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  When you, on a small scale in a grow room or a small glasshouse or polytunnel,
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  then you probably want to empty your reservoir, your tank,
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  after you've done a grow and scrub it down, remove all the biofilm and algae
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  and empty all the algae that might have formed and growing in this solution
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  and then sterilized it with you know you could use something that was.
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  Compatible with the tank or the reservoir you're using
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  and you could use something like peroxide or
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  bleach or anything like that and then when you're growing you could
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  add a small amount of peroxide as well but if you get when you
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  get larger and larger reservoirs and larger grows
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  then you can't just dump all your water and all
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  your fertigation solution because you cost you a lot of money to put that
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  water in there to build the reservoir and to store
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  it and you can get fined for
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  certain areas for for doing that so
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  we'll talk about different options you've got so if
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  you run a hydroponic setup for any length of time you've probably seen slimy
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  green film creeping across your reservoir clogging your lines that's because
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  algae thrives in nutrient rich water especially when it's exposed to light and
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  it's often very difficult to prevent that exposure to light.
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  Small tanks in hydroponic systems might have a cover on them,
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  but there will still be a vent to allow air to circulate to get oxygenation.
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  And so some light will always creep in.
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  And algae competes with plants for nutrients, reducing the dissolved oxygen
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  level. That's critical.
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  It can even harbour pests and diseases like phytophthora and things like this.
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  But also algae is a
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  solid and it will block drippers and spray
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  nozzles and things like this in aeroponics so and biofilms
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  will build up and also it's a source of
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  contamination for issues with food safety as well so you want to control algae
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  so we talked about we talked about small scale you could dump the water scrub
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  the system refill with fresh nutrient solution and you're good to go but on
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  a large grower a large grower with thousands of liters of water which 1,000
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  litres is one cubic metre.
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  When you get to multiples of those, say maybe 10 cubic meters or 10,000 liters,
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  it's not economical and it's not environmentally sustainable.
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  So you can sterilize the system. So one of the first lines of defense is sterilization of the system.
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  And obviously, again, peroxide is the most commonly used, hydrogen peroxide.
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  There are lots of different chemicals that are called peroxide.
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  And you have to be careful because some of them are really hazardous and also bad for plants.
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  So make sure you're using the right peroxide for your
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  use the peroxide used in hair dye for example is not
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  the same as hydrogen peroxide that's used for sterilizing medical equipment
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  and things like this so hydrogen peroxide is what you want to use for
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  tanks common relatively safe option as
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  long as you don't expose yourself to the the concentrate it
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  oxidizes organic material killing the algae bleaching
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  it so it'll go white and many of the pathogens as
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  well so it breaks down quickly which is both a good
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  thing and a bad thing because it obviously is not going to have residual action in
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  warm alkaline conditions that's going to be much much faster and it'll bubble
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  and it'll fizz in nutrient rich environments it'll also be faster so you might
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  need frequent dosing and you might even need a continuous one the other option
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  is something called periacetic acid.
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  And or periacetic acid often used in commercial operations it's effective against biofilms and,
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  has minimal harmful residues, it's a bit longer residence time than hydrogen
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  peroxide, and requires careful handling and dosing equipment for if you're going to use parasitic acid.
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  It also might be corrosive to any of the tank materials you're using,
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  so just be careful of that.
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  And another option is chlorine dioxide.
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  So chlorine, as we know, is a powerful and effective disinfectant,
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  particularly in well-controlled dosing systems, it can be used.
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  However overuse can harm plant roots
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  and it's regulated in some regions as well the use
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  of chlorine so you might want to use one of those three
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  chemical options or a combination of them in certain situations and things like
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  parasitic acid might have an influence on the ph chlorine and hydrogen peroxide
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  probably not going to affect the ph but it might affect nutrient solubility
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  and things like this. What should you avoid?
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  So what sort of sterilization materials would you definitely avoid?
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  I would avoid any copper-based algicides.
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  They're sometimes suggested, but in hydroponics, they're going to be toxic to
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  plants and they're a heavy metal that will accumulate in the produce.
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  So I always avoid copper.
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  I hate copper, even though it's classed as organic. It's stupid chemicals,
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  should never be classed as organic.
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  Again, you're going to avoid bleach, so sodium hypochlorite.
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  Two reasons there. Bleach has got sodium in, and so that's directly toxic to
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  plants, and also it's going to raise the pH. Bleach is alkaline.
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  So avoid that, and then avoid any what are called quat-based disinfectants.
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  These are residual disinfectants.
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  They might last for a long time. They might keep algae from being in your reservoir,
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  but they're also going to poison your crop and also potentially poison your
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  consumers of your produce.
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  So you don't want to be using any quat-based algae destroyers.
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  There are unfortunately some products probably sold by people who don't know
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  how stupid they are selling quat-based disinfectants for algae control in hydroponics in the UK.
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  I wish those people would stop or realise how stupid that is.
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  So there are a couple of organic or non-chemical solutions that I do recommend.
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  If you go to Holland and you go to say Greentech
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  or you go to some of the large greenhouses there you'll see ultrasound used
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  it's an exciting fairly new technology where
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  ultrasonic transducers and create
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  microscopic bubbles that collapse the algal cells
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  nearby disrupting their ability to photosynthesize and reproduce so these devices
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  run continuously in the reservoirs the large reservoirs reducing the algae growth
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  without introducing any chemicals and they work best in relatively clear water
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  so they can't work when there's already an infestation.
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  They'll be seen used increasingly around large-scale greenhouses and they'll
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  often have bright-coloured buoys holding them up in the water so that's how
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  you'll know that they're there. And then.
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  Lastly is the option that Eutrema manufacture. We manufacture a chitosan solution.
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  It's a polysaccharide. It's a naturally cationic polysaccharide,
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  one of the very few in nature.
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  And we have a very strong concentrate. There are a few chitosan products on
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  the market already. We're not the only ones.
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  However, a lot of them are weak as pish, as they would say in Scotland.
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  Ours is 5% or 6% solution and very.
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  Very long polymers, which makes it great for
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  flocculating algae which means all the algae come
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  together and form a big clump and then
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  you simply you put that through a
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  filter or you sieve it out with a
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  a net and all the
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  algae is removed so it doesn't destroy the algae you're not
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  getting a brown a black sediment on the on the bottom you're just
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  pulling that out not my cup of
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  tea over that's as i'm demonstrating with my hands on an
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  audio podcast pulling algae out of a pond
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  so we use it as a we sell it as a pond flocculent a
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  lake flocculent but it can also be used in in these sorts of
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  systems really good for an organic way to
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  remove algae without using harsh chemicals or
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  needing to invest in serious amounts of
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  money in an ultrasound system the beauty
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  of this is that you can remove the biomass from the
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  from the system whereas if you're using hydrogen
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  peroxide and bleaching the algae the algae is
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  still there and it's just going to fall to the bottom as black
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  sludge and then those nutrients
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  will cycle again and again and again you're actually removing
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  the sludge and the algal biomass whereas you use chitosan to flocculate it into
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  big clumps then you will see that and it works pretty much instantaneously and
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  it's a good visual way to remove algae because you just simply it happens before
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  your eyes and it and the water goes clear so it's really good really ungood there so.
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  Yeah we definitely recommend kitesan we sell a lot of it this time of year august september,
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  really hot summers they've built up algae levels are built
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  up to the point where fish if there's any fish in any reservoirs or ponds then
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  they start to really suffer health issues and so we use kitesan it can be used
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  in aquaponics as well because to remove algal blooms because it's organic as
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  well a lot of aquaponic farms are organic so they can be filtered out or allowed
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  to even settle but we don't recommend that.
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  Leaving the clear water behind. It's non-toxic to plants, biodegradable,
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  and can even stimulate plant immune responses because the cactosan can be used
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  as a biofungicide if it gets into the hydroponic system.
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  So it's a really good way to stimulate plant defense responses as well.
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  Double bubble. And some people are using that as an integrated management system
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  alongside other forms of treatment for the water.
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  So UV or rozone treatment will also kill algae as well and pathogens so also
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  look at those systems in a small-scale
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  hydroponic system a uv or an ozone treatment will also kill algae.
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  And they're also used in hydroponics, but sometimes they're just not good enough in the reservoirs.
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  So the UV is great, but the UV beam, if it's too cloudy and too much algae in
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  there, the UV won't get very far.
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  And so you'll hit the first algal cell, but it won't penetrate further beyond that.
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  So if it's a really thick, cloudy solution, it won't work.
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  And then the disadvantage of ozone is that it can
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  lead to some of the nutrients falling out of the solution because ozone is
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  a very active form of ozone like hydrogen peroxide and
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  so you can get some negative interactions with the chemicals there
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  so and also it's it's expensive
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  to treat very large volumes so there's lots of different options i wouldn't
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  say there's no silver bullet because some systems will work and some system
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  it will be best for yours so if you've found another way to control algae that
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  you think you're right to recommend then you know drop us a line drop us a DM,
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  an email at hydroponicsdaily.
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  If you go to the Utrema website, any of the contact details there will eventually find their way to me.
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  And we've got really good technical support and any questions we're happy to add.
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• 12:02
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  in our portfolio as a thank you so that's been hydroponics today for today tomorrow
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  i'm going to go do a really deep dive into cultivating plants on mars,
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  and i'm going to do a video to back it up as well on youtube so look really
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  looking forward to that because there's lots and lots of things to discuss so
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  yeah should be a good one nice long podcast for you on a bank holiday monday
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  as it here is here in the uk august bank holiday okay thank you very much for
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  listening until tomorrow goodbye.