Full Fish Ahead: Part 2

Things are happening in Avalus’ new aquarium. Let’s join him to see what’s up today.  (Note: The last photo in this post was omitted in error when first published. It has now been reinserted with my apologies to Avalus.)

Part 2 – Life in the Shell

The water in the new tank slowly clears up, the next plants and the filter are underway to my vendor and so it’s time to find a nice leaf lay down and relax.

Corydoras Panda enjoying the safety of a walnut leaf in my other tank. Yes, I have quite some green filament algae. ©Avalus, all rights reserved

In the new tank, we can see algae growing on the wood and producing oxygen. But their reign is short, they will soon be overgrown by sessile filament algae.

©Avalus, all rights reserved

The Javamoss (Taxiphyllum) is bonded to the wood, it will attach itself over time to the surface. In the foreground is a tiny bucephalandra I got from a friends tank. These tiny bulbs took over half a year to grow. The blotches are unfocussed Daphnia.

I also found three or four young pearl shrimps that must have clung to plants that I took from my shrimp tank. A young striped green platy likely got caught in the net when I fed Daphnia from the new tank to the fish in the old tank. All the unintended new inhabitants look healthy, but are camera shy.

Now for some reader interaction. Fusilier wrote: Usually with teeny snails everywhere.

Well, the physidae and the different ramshorns are getting it on.

Physidae, getting it on. A lot. ©Avalus, all rights reserved

©Avalus, all rights reserved

Every circle is a patch of eggs that I want to avoid while cleaning the glass. And there are many more on the other three panes. And probably on the stones and wood and … you get the idea. So let’s have a closer look at these lovely critters at different stages of their development.

Soon after the sexytime, we get patches of eggs:

©Avalus, all rights reserved

Daphnia are unimpressed with ramshorn eggs

©Avalus, all rights reserved

A few days later, we start to see some development. The dots became tiny spirals.

©Avalus, all rights reserved

And now after 4-5 days, there are about 40 tiny snails visible. Everyone is smaller than 1 mm.

©Avalus, all rights reserved

Freedom! After eight long days, they gnawed through their protective gelatinous shell.

©Avalus, all rights reserved

A tiny posthörnchen (ramshorn), ready to take on the world. Or at the least anything tasty that does not run away. The Daphnia are still unimpressed.

How fishkeepers got in trouble with the EU:

On the 1. January 2015 the EU enacted a decree about the prevention and management of insertion and spread of invasive species from foreign habitats. This includes a list of species that were from that point on forbidden to import to and sell within the EU borders because their danger to natural habitats. Breeding of these species and owning them is technically forbidden as well, but usually not enforced. For the interested, you can find the decree Nr. 1143/2014 on the EU websites. The list was amended in 2016 and 2017 and at the time of writing contains 49 entries with a few more likely new candidates to be added in the future. I will not argue about the tenor of the decree as a whole, but we do find a few fishkeepers favourites on the list: the plants Cabomba Carolina, water hyacinths (Eichhornia crassipes) and Myriophyllum species. These plants started appearing in many bodies of water throughout the EU, thriving, along with many tropical fish and snails. How did they end up there?

Mostly, it was people dumping the fishtanks they did not like any more in ponds or streams, plants, fish and all. In the warmer parts of Europe, winter does not kill these neobiota off, so they thrived and got noticed there first. Even in Germany, there are now stable populations of guppys, mollies and other tropical fish, usually in the waste water of power plants but also in geothermally heated ponds and brooks. A well-studied example in Germany is the brook Gillbach, a small stream that is heated by a coal powerplant. It was studied by Ichthyologists and the resulting study is open access, so I link it here: https://royalsocietypublishing.org/doi/10.1098/rsos.170160 [1]

These species have impacts on their new habitat. They carry new parasites and compete with local animals and plants for food and space. Even small animals like gobys can have large impacts, as they go after the eggs of other fish and amphibians. Mitten crabs are burrowing through dikes and polders. And the fast growing water hyacinths and Elodia species have had impacts on shipping by clogging up channels. With the intensive shipping use, agricultural and industrial runoffs, waste and climate change, aquatic habitats are already experiencing lots of stress, adaptive neobiota can just push them over the edge. Invasive neobiota are of course not only an EU Problem, it is a worldwide problem. One of the most noteworthy examples of the recent past is the mosquitofish, gambusa affinis, which was deliberately spread to combat mosquitoes and malaria.

So, as hard as it sounds, if you stop having a fishtank and find nobody to take care of your exotic animals and plants, you have to kill/compost them.  I get very angry with people that do not think or care about that responsibility they took on when they got the aquarium. Now they just want to get rid of their nurselings and don’t care about the consequences.* Just as you should not release cats, dogs or other larger animals, it should be common sense. A related bad habit is flushing unwanted water creatures down the toilet. Absolutely cruel, don’t ever do that!

In closing, I am curious how nature will adapt and if the measures taken based on the EU decree will improve the situation. Be a responsible keeper.**

Next time, I will rant something positive!

Lit: Lukas JAY, Jourdan J, Kalinkat G, Emde S, Miesen FW, Jüngling H, Cocchiararo B, Bierbach D. (2017): On the occurrence of three non-native cichlid species including the first record of a feral population of Pelmatolapia (Tilapia) mariae (Boulenger, 1899) in Europe. R. Soc. open sci. 4: 170160.

*Sidenote: Avoid diving too deep into (some-most) fishkeeper forums. Some people even brag about releasing their ‘old, boring fish’.

** I can only read this sentence with the voice of the Dungeon Keeper narrator in my head.

Link to Full Fish Ahead: Part 1



  1. voyager says

    Very interesting, Avalus. In North America and particularly the Great Lakes we are having problems with invasive zebra mussels and Asian carp. The population of carp is growing quickly and threatens many native fish stocks.

  2. says

    The invasive parthenogenetic marble crayfish was also released from an aquarium, and it is a big headache in worldwide now.
    Many invasive plant species around the world started their “career” as decorative plants. It is very important not to add to the strain on the environment through our hobbies..

  3. lochaber says

    There may be more effective methods recommended now, but the one I remember is to let plants/algae/moss/etc. thoroughly dry out for a few days before putting in the trash/compost.

    I’ve sometimes gotten those Physidae snails when starting an aquarium (probably hitchhiked on plants), but I didn’t know the name. Sometimes they can get fairly large, and they look kinda cool, like their flesh is infused with glitter.

  4. avalus says

    All: Thanks. Yes, there are many examples of invasive neobiota. It is interesting and somewhat scary to learn about them, so thank you for yor examples.

    Voyager: Thank you for your work!

    Charly: Exactly!

    Abbeycadabra: I can only write about German rules here, other rules probably exist in different countrys! Usually the department of agriculture, livestock or fishing sets the rules for how to humanly kill animals. In Germany vertebrate animals in general have strict rules to minimize pain. So for fish it is either a cut through the neck or a stab through the heart (for larger fish). Invertebrates are not subject to these rules, the rules recommend dropping them in boiling water (this is forbidden for vertebrates and I don’t know if thats really humane. With the small bodies of aquarium inmates, maybe?). A different possibility that is suggested, is to stun the animals with clove oil and then quickfreeze the incapacitated creatures.
    These rules are apprehended from commercial fishing, which is why poisoning is not listed as an option.
    Plants should to be dried and disposed of. Composting is also legitimate.

    Lochaber: True physidae are very similar to other pointy freshwater snails and I can hardly tell them apart. They *can* be differentiated by their feelers. The feelers of the lager ones look like yodas ears, they are a different ‘kind’. True Physidae have very delicate threadlike feelers like ramshorns.

  5. says

    That’s a cool tank and shows the amount of knowledge you need to make it work.
    As for invasive species, that’s a whole ‘nother powder keg we’re sitting on. One of the most common wild flowers we have here is American goldenrod which often takes over habitats that used to have a specific plant-feeder relationship.

  6. Nightjar says

    This is so cool, Avalus, I will be looking forward to see how your tank evolves! It brings me wonderful childhood memories of staring at my cousin’s aquarium for hours, it was so relaxing. I used to help him with maintenance when I was kid, but sadly I never took up his hobby and he doesn’t keep fish anymore (he gave up on it when his wife became sick with cancer, and gave everything to a friend). I often wish I had an aquarium in my life to stare at these days, few things are as relaxing as that was.

  7. rq says

    This is so cool, watching the development of a small ecosystem! Small, yet complex.
    Also I think my favourite parts will be your closing rants, a nice opportunity to learn something completely new about a field I am completely unfamiliar with.

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