Plankton trawl and Seaweed Update (Jun2015)

During one of my last Kayakfishing trips I tried something new. Plankton trawling.

I bought this Plankton net for kids, it was all I could find that wasnt ridiculously expensive. Didnt expect anything from it to be honest but it worked absolutely brilliantly.

I thought I would be trawling this around for half an hour with the kayak but that isn’t really possible. The net has so much drag you literally paddle on the spot. Usually I use a sea anchor for fishing which is like an underwater parachute that slows down the drifting of the kayak due to wind. So instead of the drift anchor I just used the plankton net as my sea anchor while fishing. The drift over ground was really slow at around 0.5-1.5kph I think its critical to use the net very slow as otherwise the pressure inside the net is so large that it squashes the plankton. I would be interested (and please feel free to comment) if anyone has experience with plankton netting as to what speeds are used commercially or for research in larger nets.

Anyway now to the interesting stuff. After every few minutes or drifts I check the net. A small plastic inspection bottle is attached to the bottom with built in “magnifying glasses” its better than nothing but obviously rather useless. Its enough to see that you are catching something and I added all the catches in a container to bring home.

Here some pictures of the haul. Keep in mind this was only roughly half an hour of drifting with this net close to the surface in 12m of water. Its totally mindblowing how much I was able to catch!

One creature that always stood out looks to me like a Lobster, it had (with bare eye inspection) all its features. There was also tiny jellyfish, tons of copepods and some worm like moving things and tons of other things I just couldnt identify, it was amazing, felt like a child 🙂 The amount of live from just trawling for half an hour at ~1kph seemed unreal to me.

If I had the chance I would love to just leave it all in a tank and feed phytoplankton to see if any of them will make it to their next stage.

One in particular looked really cool and as Roxanne (my girlfirend) pointed out most likely a Siphonophore (An Animal colony closely related to jellyfish and corals), propulsion in the top part and tentacles in the lower section, which was about 5cm long but broke apart when transferring.


Copepod Culture

My humble, very boring to the above, plankton breeding culture is working great but I have to be more vigilant in feeding and cultivating phytoplankton. If you keep feeding it to them they just keep multiplying and are a good foodsource especially for those picky feeders and fish with small mouths like pipefish etc. This is about half of the copepods from the 10 litre culture I have going. The culture is just a big (15l) plastic container with a heater, IKEA reading LED light and an airstone.


Seaweed Updates

The Kelps and other seaweeds are doing great at the moment and its so great to finally actually having to trim and remove big pieces to keep the tank tidy.

Red microalgea still around but definitely kept in check compared to last year.

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Some Reds shooting up but growing very slow.


The Rainbow Wrack is also growing slowly but older parts are being taken over…


The Sugar Kelp grew from L15cmxW6cm to over L90cmxW22cm which is just fabolous! Kelp has slowed down a bit and is being eaten in parts.


and here a cutoff piece of a sugar kelp…its nice to remove that amounts of biomass from the tank (removed about twice that amount previously)


Also most excitingly (as I havent added this species) new shoots of Felty Fingers Codium Fragile (one of my favourites) coming up in rather weird places.

On top of the Turban Snail…poor fella is going to regret not keeping his shell clean once the Felty Fingers grow bigger 😉

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On the Powerhead…(yes this IS a powerhead 😉


And finally on old rock that is there since nearly two years and never had Codium on it…


Keeping this short, soon another post to come on updates of animals…


9 thoughts on “Plankton trawl and Seaweed Update (Jun2015)

  1. Hi Marius,

    die Haftkrallen des Zuckertangs sind ja ein Traum – genau wie im Meer!
    Sind deine aktuellen Makros alle unter Tageslicht-LEDs gewachsen ??

    Lieben Gruß

    • Hi Edwin

      Ja das ist sehr wchoen zu sehen und der Wachstum ist extrem. Hab noch nie sowas erlebt in diesem Aq.
      Ja ich hab immernoch nur die Aquaray 6500 led. Glaube es sind 54w total.

      Viele Gruese

  2. Tank looking good Marius. On the subject of plankton, if added to your main tank, is there the possibility of unwanted creatures surviving and becoming a nuisance? I ask as I spotted those plankton nets on Amazon, and had the same idea as yourself. I was going to pick one up in America in October, (ridiculous postage otherwise)

    • Thanks Peter. I added a whole bunch of it to my tank and haven’t seen anything surviving. Most of it is probably eaten very quick anyway which is not a bad thing either. Not sure what could end up as a nuisance except crabs that could go undetected for a while? The one i got is from eBay for around 35 euro. Put plankton net into the ebay search and you should find it straight away. It’s very interesting to see what crazy stuff shows up in it! Have fun 😉

  3. Hi Marius,
    tank is looking lovely! The sugar kelp seems like a very good species to have, it also worked quite well in my tank. I like all the encrusting corraline algae you have as well. The plankton project is very cool, I just found the following link, perhaps of interest: The plankton cultures are great, really a must if you are being serious about the hobby. I just do not have the time/energy/patience to do it at the moment, so i will stick to fish that I can feed prawns! cheers, Mick

  4. Hi Mick,
    Thanks. Yes its was going well now with days getting long its not growing as fast anymore but certainly a good addition to reduce nutrients. The Corraline Algea is going like that since the beginning, Its coverage on the shore here is very strong too.
    Thanks a lot for the link will have a closer look at it. A very good find! I would have loved to spend more time identifying all the stuff I found but time is always the issue 😉
    Cultivating copepods isnt that much work expecially if you have the phyto culture along side it but I didnt spend the time on it too lately and ran out of phyto. Might get more into it again during those rainy winter days. Feeding prawns is surely the faster option and they all love it 😉
    Good Luck

  5. Pingback: Summer Tank Update (Oct 2015) | Irish Rockpool Aquarium Adventures

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