Category Archives: Coldwater aquarium

Army of snails

It looks like I have cracked the code to a less algae infested aquarium. I have had lots of snails before, but I realised that I might have underestimated how many snails there are in natural conditions. Therefore I brought home a  lot of snails, around 150 common periwinkles, and the result is so far good. In little over a week they have really grazed down a lot of the green algae and the rocks are starting to show through. The pink coraline algaes are also visible now. This is the “after” photo. Unfortunately I do not have any “before” pictures.

After adding 150 common periwinkle

Full tank photo after adding 150 common periwinkle



Happy New Year – not much has happened in the tank. Project baby has kept me busy, but now it pays of. The aquarium is a great baby pacifier and now little Sigrun is big enough to sit herself in front of the tank.

Still struggling with high nitrates (around 15 mg/l) but the phospates are reduced from 0,3 mg/l to 0,1mg/l. The coralline algae is starting to show through the thick carpets of green and red algae. The sharks are thriving on Mysis and small herring.

Baby sharksShark TVPlease dont disturb I am watching sharksBaby sharks


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System overload 2 – update

This is getting weird – I sent a water sample to my local (1 hour away) saltwater aquarium store. He phoned the results:

Kh 15 – which is not that wierd since this is the same as the tap water (lots of calcium)

Nitrates > 25 mg/l !!

Phosphates 0,3-0,5 mg/l !!!! which is really weird since I measured around 0,3 before the water change

My own test-kit (Red Sea algae control test kit) measured nitrates at around 2 mg/l and phosphates almost 0 – so now I am confused, since I just changed 600 liters out of a total of around 800 in the whole system. I ordered a new test-kit for phospates – hope that will give me some direction off where my aquarium is headed.

Today I built my own design of a portable deep-sand bed, using a box for refrigerators from Ikea, some pvc pipping, parts from a gravel bed filter and a piece of  nonwovens (textile for preventing the sand from running out the drain in the bottom). I hope this will help reduce nitrates by denitrification.

Here a schematic of the whole system as it runs now.

Schematic with flow and filtersIkea bow with two drains, seen from the sideTwo drains seen from insideOne drain coveredSand and second drainFinished filter
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System overload

Guess I was too optimistic about how many fishes the aquarium could house. I have measured nitrate and phosphate a couple of times the last months and they were at a steady high despite using rowaphos  and reef pellets for removing nitrate. I have added a reactor chamber run by a small eheim pump (around 400  l/h), but it did not help much, nitrates where still around 2-4 mg/l and phosphate around 0,4 mg/l.

So last weekend I changed 600 liters of water and cleaned the sump and the upper filter aquarium. It also seems that the upper filter aquarium did acts as a filter as I hoped, so I removed some of the live rocks and placed them in the  sump. Now the upper aquariums acts as a crustacean zoo, with at least 4 species of crustaceans, to keep them from eating my snails and being eaten by the turbot.

The turbot by the way ate the  small lumpsucker after just one week. After the water change the nitrate  and phosphate is much lower, the big fishes are gone, so I hope that will help.

Here is a photo of the upper filter aquarium and one of the squatlobsters.

Full view of top filter aquarium 1,7 m longSquatlobsterReactor with quickphos phosphate remover
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The cod finally got to big for the aquarium – mostly because it eats more than the filters can handle. The two sculpins where put back into the ocean.

Instead I caught a lumpsucker, shrimps and thousands of mysis to feed the shark babies. I now have three newly hatched sharks and a small Greater weever.

Below are pictures form my collection trip when I caught the Greater weever and msyis caught during a night dive. Mysis gets attracted to the light form the dive torch and are easy to scoop up with fine-mesh net in front of the light.

Flatfish front onGreater weeverthe one-eyed-turbotJellyfishSaithe caught in a netGreater weeverCommon shore crab feasting on a dead sculpinCod and sculpins going back to the oceanGreater weever and shark side-by-sideMysis aka. cloud of food
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Aquarium final finish

The aquarium is finally done. I have been discussing the frames and hatches a lot with the carpenter and we ended up doing it in aluminium and acrylic plates. The plates are fixed to the wall with velcro glued and nailed to to wall. It think is looks great with a nice minimalistic touch. And most importantly it is easy to access the aquarium. Yesterday the two shark egg hatched so now there are two very small almost white sharks in the tank.

FrontFull tankFull tank from the sideBaby shark
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My tank has got new sharks small-spotted catshark (Scyliorhinus canicula). Sharks are my favourite fish, since they reaylle act and look like the predator they are and they seem to have a bit more personalty than the always hungry cods. Three eggs are waiting to hatch and one has already hatched. The hatched one likes to eat small herring and mysis, so for now it is growing fine.

Here is a photo of a shark embryo waiting to hatch. Its fine brushlike gills are clearly visible and the eyes is very large already.


Scyliorhinus canicula

Scyliorhinus canicula

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I hoped a lot of water would ease the problems with high nutrients, but I had a few deaths among the fishes and feeding the to much. So now the algae has taken over.  I changed half of the water in the aquarium, which reduced the N and P somewhat, but the rocks are still covered by red slimy algae. The next step will be to add a filter with phospate remover like Rowaphos. I´m still trying to work out how to build a nitrate reducing filter. Meanwhile I have added a small army of snails. Now I have chitons, limpets, flat periwinkles, edible periwinkles, topsnails and a few blue rayed limpets.

Here´s a photo of the front glass. A week after I introduced the snails the glass was cleaned.

Snail army

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the perfect food for the coldwater aquarium

On a diving trip too Sweden I stumbled upon the perfect food for the aquarium – tiny herring. They were sold in a supermarket as bait-fish. I have tried using white-fish bought from the aquarium stor before, but they apparently smell wrong, my fish does not react to them. But herring make them crazy. The cod ate 4 in 2 minutes!

Here is “Torben” as we call to most aggresive of my two cods after he swallowed his 4th herring:

cod feeding on hering

The sculpins where not as fast in getting to the herring, but when the hermit crabs started to move them around the sculpin moved in.

2015-03-01 19.41.01

2015-03-01 19.42.192015-03-01 19.42.262015-03-01 19.42.292015-03-01 19.42.35

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Collection trip – Swedish west coast

The cold does not prevent the collection of new creatures for the tank. The first free dive this year was a good opportunity to collect sugar kelp, snails, spider crabs  and hermit crabs for the tank. My dive buddy was lucky enough to catch a Fivebeard rockling. The trip went to Hamburgsund on the swedish west coast. The sandy bays and rock shores are fantastic dive sites and during night the rocks are crawling with crustaceans. In the shallows you meet flatfish and seatrout. Unfortunately I had some technical issues with the underwater camera, so I did not get as many photos as I hoped, but here are some of them.


Hermit crabs


Plumose anemone (Metridium senile)


Hermit crab with a shell covered in small polyps, probably Hydractinea echinata


Calcareous algaes, Irish Moss (Chondrus crispus) and breadcrumb sponge (Halichondria panicea)


Great spider crab (Hyas araneus)

Great spider crab (Hyas araneus)

On a more depressing note, the trip really showed how we are slowly  destroying the ocean with plastics. The winter storms has carried tonnes of waste to the beaches.

Plastic sea


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