Can I control these populations?
I have a Fluval Roma 240 aquarium in which I have had an explosion of shrimp—and there are hundreds.
I do weekly water changes of around 30% to keep the water chemistry stable and clean out the filter once a month, this is where my problem starts. Despite putting a fine net over the filter intake, the Fluval 406 filter still makes a lovely home for a lot of shrimp. I clean the filters out in a 25-litre bucket of aquarium water and then spend the next few hours catching them and reintroducing them back into the aquarium as I don’t want to pour them into the garden.
Secondary to this problem is that it’s difficult to vacuum the substrate— which is Fluval Plant and Shrimp Stratum—as the syphon sucks up tons of shrimp. I’ve tried a net on the end of the syphon, but substrate just gathers up in it and blocks it, so I’m back to fishing them out of the bucket again. I now have planaria worms thriving as I’m unable to clean the substrate effectively.
I’m intending to drastically reduce the shrimp population by donating them to the local fish store. Are there any chemicals I can use to eradicate the worms which will be safe for the remaining shrimp and my very healthy population of assassin snails?
IAN BIBBINS
NEALE SAYS: Your tank is providing enough shelter for juvenile snails, and shrimps, and sufficient algae and other small foods to keep them fed, and with plenty of food and safety from predators, they are obviously reproducing freely.
Ultimately, if you want to slow down their population growth, you’ll need to rein in the abundance of food, or else, add a predator that would control their numbers better than whatever community fish you have.
Regulating the amount of food is more difficult to do, and may take some time to have an effect, but longer term, can work well. Essentially, it means keeping the tank cleaner, so there’s less algae and organic detritus, while also reducing the amount of food put into the tank, so there’s less available to the shrimp. Over time, if you remove surplus livestock, they won’t be replaced as quickly, and you’ll get the result you’re after.
Flatworms – and pest snails – are best regulated in this way too, but you will need to be ruthless about physically removing them on sight across the next few weeks. Cull them back far enough, and then reduce the amount of food. This will limit their ability to reproduce, and you should find their population stabilises low enough for you not to even notice them.
Flatworms may be killed with anti-worm medications such as praziquantel, but killing large numbers all in one go does mean your filter will have to work much harder processing all the extra decaying organic material their little corpses create, so that’s a ’nuclear option’ I’d tend to avoid if at all practical. (Editor’s note:
Genchem’s No Planaria is also a safe way to eradicate planaria from shrimp tanks, and contains betel nut palm extract as an active ingredient—but it is still a ‘nulear option’. At time of writing it’s available for £16.99 at aquaessentials.co.uk)
I am trying to set up a 100-litre Cameroon biotope with African fish and maybe a native killifish or two. I want to have a built-in riverbank, but this is causing me a bit of trouble. How would you recommend I do this, please?
MAX GIBSON
NEALE REPLIES:
When building riverbanks, it’s a good idea to use a gravel tidy above a layer of sand or gravel first. This creates a buffer zone between any rocks you later use and the glass floor of the tank. If there’s any slippage, the rocks will press onto the gravel tidy rather than the glass, making it much less likely that they’ll crack the tank. Then you can use rocks of different sizes to shore up the substrate used for the riverbank. Alternatively, you can pile rocks into the appropriate shape on top of the gravel tidy, and then fill the gaps with sand and gravel.
The problem with riverbanks in aquaria is that, over time, they tend to subside and level out. Plant roots are useful for securing them, and to some extent, plants help to make riverbanks stable in the wild too. Slates are useful when placed more or less upright, as they naturally form little shelves, but I don’t think they look good mixed with waterworn boulders, so if you go down this route, you may well need to restrict yourself to slates and slate chippings for the rest of the rockwork.
Often, the more hardcore aquarium builders will create a stable superstructure from things like expanding foam and lava rock, using silicone sealant to hold everything in place. This can be a massive and expensive job, but the results can be stunning. It would probably be overkill for a small tank though.
Of the African plants regularly traded,
Anubias are the most common. Other species you might see periodically include the reliably hardy Crinum
calamistratum, the fern Bolbitis heudelotii, the bushy stem plant
Ammannia crassicaulis (although that requires a lot of light to do well) and Nymphaea water lilies. Bear in mind that these species don’t necessarily inhabit the same sorts of places.
Anubias and Bolbitis are adapted to growing on solid surfaces, so you’ll want plenty of rocks or bogwood for them.
Crinum look a lot like onions, with a bulb that does well only partly pushed into a rich substrate, such as gravel mixed with laterite or some other aquarium soil.
They are adaptable and undemanding though and will grow in plain sand or even gravel if given fertiliser pellets now and again. All three genera appreciate water current, so they’d be good picks for a rocky or gravelly stream biotope. Since Anubias and Bolbitis especially are plants of the riverbank, attaching them to rocks or bogwood pieces pushed into a sloping bank of rock and gravel (or sand) could look brilliant.
Nymphaea water lilies, on the other hand, prefer less flow and are more for biotope tanks based around a pond or ditch. In this instance a muddy substrate, lots of leaf litter, plus some twigs and choice pieces of bogwood is just what you’d want here.