Locally sourcing is all the rage in groceries, so why not fishkeeping too? Gabor Horvath sets up a tank based on the local seaside.
It has been my long-term ambition to observe the everyday life of local rockpool creatures in the comfort of my house. I’ve spent many hours watching the hustle-and-bustle of small pools on the South Wales coast. However, I missed the close, intimate contact you have with creatures kept in aquariums.
I’ve seen crabs, fish, shrimp, anemones and even starfish in the wild. However, this is mostly as a quick glance before they disappeared under a rock. While such fleeting meetings were all well and good, my inner aquarist wanted more.
Related article: Go rockpooling this weekend.
What size for a rockpool aquarium?
The first thing to decide was the size and type of the tank. In theory I could set up a rockpool tank in a relatively small aquarium. However, keeping tiny water volumes consistent can be problematic.
As the chiller I planned to use can handle aquariums up to 500 litres (110 gal), I wanted to go larger. Plus, a spacious tank allows more creatures – including fish – and provides a more stable environment.
My plan was for a ‘proper’ marine setup with a sump. I went for a TMC Reef Habitat 60 aquarium with an iLumenAir 600+ light, kindly provided by TMC. I already had a TMC Reef 2000 pump which was the perfect size for the set.
I filled the filter chamber of the sump tank with filter wool. The return pump, and the additional pump for the chiller, had their own dedicated chamber. The outflow pipe from the chiller is next to the intake of the return pump, so it can push the cool water up to the rockpool display straight away. This maintained a temperature of 17.5°C (63.5°F).
I installed a SICCE XStream SDC wavemaker pump to create intermittent currents to stimulate waves hitting the rockpools. I decided against using a protein skimmer. I planned to keep the bioload of the tank low and hoped that excess nitrates would be used up by the seaweeds.
Aquascaping a coldwater marine aquarium
Most of my local rockpools have a sandy bottom. So I searched for a local company that dredges sand from the sea and asked for a bag from their latest excavations. It was surprisingly clean so it went straight into the tank.
I added Prodibio Start-Up bacteria to speed up the maturation process and soon it was time to add some live rock. It sounds easy – you could say just pop down to the seaside and grab some – but it’s not that simple.
Under the Coast Protection Act 1949, the removal of any natural material from public beaches in the UK is illegal. This includes sand, pebbles and rocks. Always ask the local council (or whoever owns that particular shore) for permission if you do intend to use materials you find.
The area I planned to collect my rocks from is frequented by fossil hunters, so the council isn’t too twitchy. Having the necessary verbal agreement in place I popped down to pick the rocks.
I began my search for small sized pieces with various young seaweeds and other algae attached to them. Young plants adapt better to new environments, so I advise you to do the same. I managed to collect several different species, including sea lettuce (Ulva sp.), bladder wrack (Fucus vesiculosus) and coralline algae. I even found a single rock with six different macro algae attached to it.
Many rocks had anemones, too, so they were the first animals introduced to the tank. I also collected painted topshells (Calliostoma zizyphinum); an excellent cleaning crew, keeping the glasses almost completely algae free. The only issue with them was that from time to time one of them decided to climb out of the tank to
After getting home the rocks were arranged so that the tank could be viewed from the front and from one side. I intentionally didn’t wash the rocks as I wanted to preserve every life form on them. Once the silt settled I began discovering my own rockpool.
The first revelation was the abundance of micro-life on the rocks and seaweed. Almost invisible to the naked eye, the macro lens of my camera revealed a brand-new world. My tank was now home to several species of feather worms, barnacles and other minute animals.
Selecting life for my rockpool
Some of the rocks came with the bonus of having beadlet anemones (Actinia equina) already attached. However, they were all the usual red type. They looked great but I wanted diversity so planned to collect some other colours.
I also hoped to find other sea anemone species but I couldn’t find any in the target area. The vibrant snakelocks anemones (Anemonia viridis) would look great in a tank if you can find them. Neither could I find common hermit crabs (Pagurus bernhardus).
What I found was a great number of shore crab (Carcinus maenas) in various sizes. As they’re aggressive and destructive I didn’t want to add any. However, when I saw an interestingly coloured white marble-patterned tiny crab I couldn’t resist.
Later I realised that it was a mistake as it grew quickly and began to rearrange the decoration. I removed it to the sump tank, where it happily lives ever since.
By combing the undersides of the seaweed-covered rocks with a net I caught several common prawns (Palaemon elegans). I selected a few larger females and a couple of males (they are usually smaller and thinner than their partners).
I also caught half a dozen smaller brown shrimp (Crangon crangon) which was no easy task. They hide in the sand with only their eyes and antennae poking out – I had to scoop up a large amount of sand with the net and then sift it through.
While I was busy catching shrimp my daughter spotted a fish swimming to under a flat rock. Two fish then darted out straight into my net. One was a common shanny (Lipophrys pholis), and the other a rock goby (Gobius paganellus). Several other small blennies and gobies live in the intertidal zones; most are hardy and adapt easily to aquariums.
Looking after a rockpool
The fish I took home settled down quickly and learned where their food comes from – the shanny always the first to come begging for some snack. Shannies are comical with their large ‘clown’ mouth and independently moving eyes. But, the look is deceptive: they have tiny teeth and a surprisingly strong bite.
The two gobies turned out to be both males, and it didn’t take long until they began to spar for the best spots. During the disputes the larger male turned almost black, with just a yellow edge of the dorsal fin brightening the picture. It was amazing to see how quickly they could change colour: within a minute of chasing away the rival he turned back to the regular camouflage-brown patterned look.
Feeding my rockpool wasn’t expensive or difficult. I used white fish fillet pieces as a staple with chopped mussels, cockles or raw prawns adding some variety to their diets.
For the anemones a cube of frozen Mysis or Krill was dropped in, while I added a liquid coral food for the tiny filter feeders. I fed the tank only on every other day. The shrimp dealt well with the leftovers and the snail kept the algae under control.
Maintenance was simple: a monthly 25% water change and occasional algae wiping from the front glass.
I returned to the beach at the end of August (weeks after a heatwave) to measure the water temperature. The sea temperature was 23°C (73°F), while in the rock pools I measured 24-30°C (75-86°F). This was during receding tide, only an hour after the main sea left the zone. I can only imagine how high the temperatures went during the main heatwave!
After this experience I turned off the chiller (the room temperature is around 21°C (70°F) and every creature still looks healthy. If you’d like a marine tank but want to save on heating costs, a rockpool tank is ideal for an unheated room. Best to have the chiller on standby though, just in case excessive heat does begin to cause an issue.
Related article: What temperature should my aquarium be and why is it important.
Feeding is easy (and cheap) as well as running the tank. With the light on for 6 hours the running cost is around 30p a day (+36p if the chiller is running). The food is less than £2 a month, making it an economical project. Learn more about fishkeeping on a budget.
This is usually the point where the ‘but’ comes in. I tried to find any cons for such a tank but aside from an occasional snail escaping and visiting your sofa, I couldn’t find any. I simply love this setup and it’s definitely in my top three of the many tanks I have owned in the past forty years.
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