Coldwater marine aquarium Blog 2008 July
July 30 2008

It's mid summer and the tank has taken the rather woolish, brownish look that it has in summer. I guess I'll have to expect that since it mostly looks like that in nature too at this time of the year. The growth of all types of algae is great. I constantly have to export biomass to prevent the tank to get too full. The algae that grow fastest are the seasonal summer species, inlcuding my "weed" which is probably Pilayella or Ectocarpus. But all the other ones are growing too. The permanent nice looking algal undergrowth is really taking shape. I just raised the temperature to 18C, which is probably the highest I will go. I have a clear impression that temperature has an effect on growth of most of the algae. It could be that it is not just the algae that have the ability to grow faster, but also the bacteria and animals that have an ability to produce more nutrients. The high temperature probably also has an effect on the small fauna. When I switch off the wave system I can see swarms of tiny crustaceans and worms all over the tank. The fish hunt them, but I don't think they have much effect on the populations off very small animals. The small fauna is most abundant on the algae. They probably feed on the food getting stuck there or on algal falloff.

Hot summer

Early July


I June I ran out of my nice supply of self caught zooplankton. It turned out that my lucky catch of several hundred grams of Calanus finmarchicus and others was a one time phenomenon. I haven't been able to find comparable concentrations anywhere since. I am a bit sceptical to the self made blender food after having seen how well real plankton disperses in the water. The blender food sticks together in clumps. When you blend so much protein it seems to work like gelationous glue. It could be my imagination though. The blended food is probably adequate. And Eric Borneman, the coral expert who is very active in the hobby, reccomends this type of food and uses it himself. But it would be nice to have the real thing anyway. Also, my version doesn't contain any phytoplankton. I could add vegetarian food to the recipe, but will really blended large plants be anything like small single celled organisms? I doubt it, though there is a chance that the nutrient content is the same and that the clams and other filter feeders would be able to use it as a good replacement.

Still, partly for fun, I decided to go ahead and buy some pretty expensive netts from a supplier of educational equipment. Two of them are trawl nets for towing after a boat. The first attempt wasn't a success. Could be because there was very little plankton at the time. I'll have to test some more, but I doubt there will be much food out of it.


Plankton trawling

The large dominating red algae from last months update came loose and I had to take it out. It was the biggest single export yet, grown entirely in the tank. The weight is after I had twisted as much water out of it as I could with my hands.

Carbon experiment

I have a problem with yellow water. It has been there for a long time. The water is very clear after a water change, but starts getting a brownish yellow color after only a few days. Last month I decided to try out active carbon filtering. The first thing I did was to go for a cheap solution to see if it worked. I bought a cheap 1 liter reactor from Aqua medic, along with 5 liters of AquaMedic Carbolit 4mm pellets. I set up the reactor in the sump and ran the smallest powerhead on it, with some restraint on the outlet so that the flow was about 300 liter per hour. After a week I could not see any difference. Bummer. At that point I knew that carbon was not going to be a quick and cheap solution to my water filtering problems. The next step was to figure out if the carbon could have any effect on the water clarity at all. I took a glass of tap water for reference and one with tank water. I could clearly see that the water had a yellow tint. Then I tried to pour tank water from a third glass through new, rinsed carbon. After pouring slowly over carbon many times there was still no sign of less yellow. I then put a glass of tank water in a container with about half a glass of carbon, and let it sit there for some minutes, I also stired carefully a few times. Then the color was gone. There was some blackening if the water though, because of carbon dust. So I figured that maybe with some longer reaction time the carbon could work. I put one more liter in the sump in an improvised container with open top. After that I was imagining that maybe there was a difference, but I'm not sure. The water is certainly yellow still.

Water samples

Left tank water. Right tap water for comparison.

Next step in the process is to try a much more expensive and heavily powered system. I ordered a 10 liters bypass reactor from Aqua Medic, and 4 liters of Seachem Matrix carbon. I figured that even if the carbon doesn't work, I would probably need the reactor if I am going to try ozone later. Ozone is pretty complicated because you need 2 carbon filtering systems, one for the water that is treated and one for the air that goes into the room. So if I am going to try ozone later I need 2 reactors, one for ozone and one for carbon. I also need an air injection system, an air drying system, and finally an air cleaning system.


Dog whelk (Nucella lapillus)

Fish developments


Snake pipefish (Entelurus aequorus)

I had one corkwing wrasse (Symphodus melops) from last year. It had now grown a lot and was stressing up and down the glass rather than swimming around the tank feeding. I get stressed by that too so I decided to let it have its freedom back. I got a new corkwing recently so I still have one wrasse. It feels great to be able to release animals back into nature rather than have them die in the tank. I got two really beautiful pipefish, probably snake pipefish (Entelurus aequorus). One was sick from the beginning and died after two days. The other one lived for about two weeks. It ate a lot and seemed to be ok, though it had some skin problems with skin or slime coat peeling from a few places.

Did you know that it is not only the clown fish of tropical regions that use cnidarians for protection. In summer the ocean here is full of the very large lion's mane yellyfish (Cyanea capillata). Juveniles of Whiting (Merlangius merlangus) use these to their advantage by hiding among the threads. When I was on a boat trip I managed to catch two small whitings. One disappeared the first night, but the other one did well and ate a lot. Unfortunaltely it went into the overflow, sigh. Speaking of cod fishes, I also had a five beard rockling (Ciliata mustela) that I really regret putting into the tank. It was about 15 cm long and a serious threat to much of my fauna. I saw it grew so it was obviously feeding on something. It was extremely shy and never leaving the rocks in daylight. Finally lured it out and caught it after dark. Big feast for the anemones that night.


Plaice (Pleuronectes platessa)

I have added several sea sticklebacks (Spinachia spinachia), but they have all disappeared. Generally these don't seem to do well in the tank. It could be that the flow is too great for them. I usaually find these fish in low flow areas. The plaice (Pleuronectes platessa) that I caught this winter has been doing very well and is now so large that I consider releasing it back in the ocean. I recently caught a new one that is much smaller, so I'll still have one. I've had three painted gobies (Pomatoschistus pictus) for a year. Two males and a femal. The female lays eggs and the two males had caves that they protected. One of the males went into the overflow recently though. There is a new one so I still have three. I would like a few more of these nice fish. I have tried other fish in the Pomatoschistus genus. But they have vastly different personalities from the painted goby. They are much more easily startled and always end up in the overflow.

Took out one Montagus's sea snail (Liparis montagui) that seemed starved and stressed. Haven't seen any of the others since that. I assume they are dead. Haven't seen the two shannies (Lipophrys pholis) lately. I fear they have taken the overflow path. The three rock eels (Pholis gunnellus) are doing great. they have lost all shyness and are constantly on the hunt. The tank seems to be a great place for them. The two spotted gobies (Gobiusculus flavescens) are doing great as always. Two of the males are still guarding spawning caves. The ones I have are very large and old. I have gotten a few new small ones, but they have disappeared. The shoreline waters are stuffed with juveniles of this species right now. I had the oportunity to watch a few pollocks hunting gobies in shallow water. It was really fascinating. I didn't think the pollocks could catch enough gobies to live off, but with the swarms at this time of the year it seems to work.

Crab, rock eel

Rock eel stealing snacks from crab.


Rocks are getting overgrown with flora and fauna.

Back Home