It’s been a tough few weeks in the tank as half of the Sand Goby population has been wiped out (and since replaced). With the crabs gone it wasn’t difficult to narrow down the potential culprits, although in fairness the crabs never bothered with them anyway. The first three casualties were not eaten, so that was a clue. Or so I thought.
I found two of them still alive (albeit not much longer) but with what looked like a bite having been taken out of them. The other was just dead, with no sign of damage. That one may have been natural causes as they don’t live very long (between 1-2 years).
They’ve lived with my five small blennies for several months with no issues, but I introduced two larger blennies recently so I figured it had to be them as they were quite boisterous around the tank. They didn’t see the gobies as food, but they may have taken a bite out of them due to marking their territory or establishing dominance in the tank. I didn’t witness anything especially untoward, but I did see them chase the gobies away several times.
So it must have been them, right? I decided to return the two blennies to the pool I got them from, in Half Moon Bay. Problem solved. Except another one of the gobies went missing the next day, and I’m fairly sure now that the Rock Goby was the culprit all along! More on this shortly.
An Accidental Passenger
There was nothing to bring back with me, although there was one unwanted hitch hiker that came along for the ride. It must have been a good two hours before I got home and removed all the gear from the car, and there in one of the nets was a little prawn that I’d somehow missed.
I assumed it would be dead, as it had been out of water for a couple of hours, but when I picked it up it was jumping around so I quickly threw it into the tank (into the breeding net that had been used to segregate the two blennies) and, incredibly, it was fine. I kept an eye on it for a few hours and then released it into the tank, and it’s doing well, as you can see below.
Lessons in Predation!
As much as I’m loving doing this and it’s something I wanted to do for a long time, it is incredibly stressful as it’s all a learning curve. The information available online only tells you so much. For instance, Chat GPT said a three inch Rock Goby would be a great addition to the tank and would not predate on anything else as it’s still only small.
I wouldn’t have put a five inch one in there as I know that it would eat anything it could fit in its mouth. This one isn’t that much bigger than the sand gobies though so I’d never have believed it could eat one. Bully them and take a bite out of one? Possibly. Actually devour a whole one? No chance.
Yet I’m fairly sure that’s what happened. There were five sand gobies in the morning, but by the afternoon I could only see four. They’re always visible and it never takes long to find them all, so I feared the worst. ‘Rocky’ (yeah I know I took the lowest hanging fruit with that name!) was also missing though, which in itself isn’t unusual, but when it didn’t come out at feeding time I knew something was up.
Eventually ‘Rocky’ came out for the next feed later on, with a massive belly that was clearly due to it having the sand goby in there. I scooped it out and separated from the rest of the tank before it could eat anything else. Usually I’d just take it back to where I got it, but I decided on a different solution and I decided to section off the tank into two, with the smaller stuff in one section where they’ll be safe.
That took a week or so though so I kept ‘Rocky’ in a breeding net away from the other fish. I’ll update on what followed shortly.
First though I have to report on another trip to Heysham.
The Seaweed Struggle
One of the most difficult aspects of doing this has been finding and keeping seaweed. The tank looks really bare without it, but it’s tricky finding suitable plants around here as the pools are not rich with various plant life like you’ll find in the likes of Devon and Cornwall. Most of the plant life around here is brown. I briefly had saw wrack and bubble wrack in the tank, both of which did quite well in terms of not dying, but its not the most colourful and most of the time it just sank to the bottom and wasn’t flowing and standing tall in the way I thought it would. It looked a bit crap, so I returned it to where I got it (Llandudno if I remember rightly).
It needed green, so I added a load of sea lettuce recently and it looked fantastic. But not for long. I attached it to rocks with elastic bands to keep it secure and the bright colour really set everything off in the tank. It was the best the tank has looked, but unfortunately the sea lettuce quickly started to break down and pollute the water. All of the fish started scratching themselves on the gravel / rocks so I had to do a big water change and remove all of the sea lettuce.
I tried again with more sea lettuce that I picked up in New Brighton, but again that quickly started to break down so I removed it before it could do any damage. An interesting side note to this is that the second lot of sea lettuce I gathered was absolutely teeming with hitch hikers. There were several minuscule prawns and crabs that looked like they had just hatched, as well as a couple of tiny Brittle Starfish (see above). I’ve never found any of those Brittle Stars before and it would have been cool if they were bigger, but they were so small the only thing I could do was put them in the sump tank and hope they survive and grow in there.
So sea lettuce wasn’t the answer. I decided to try for something else, so I went to Half Moon Bay at low tide and grabbed some long strands of bubble wrack from the rocks, as well as some clumps of spiral wrack. The bubble wrack I tied to some small rocks using elastic bands, while I superglued the spiral wrack to some flat pieces of rock. It has definitely added to the aesthetic of the tank and provided more cover for the fish and prawns. It isn’t the most colourful though so I’m still on the lookout for something red or green just to finish things off.
Restocking the Goby Crew
On that trip to Half Moon Bay I put a couple of fish traps into the rock pools while I gathered the seaweed. I wasn’t expecting much, I assumed it would just be a load of blennies as usual, but if I could catch another small rock goby or a butterfish that would be great. And I did. In amongst half a dozen blennies in one of the traps I spotted a rock goby. More on this shortly.
I also made a trip to New Brighton to restore the sand goby population back up to nine. There are a couple of large sandy pools there which are teeming with them, but they can be tricky to catch in a net as they dart around so quickly. I scooped up one in a net but it was proving very difficult to get more.
The solution was the fish trap net, which I baited with frozen prawn and squid. I left it for half an hour and when I brought it in there were four good sized sand gobies in there alongside a crab and a load of prawns. I released everything else and brought the little gobies back, and they are all doing well. There are three males and six females in total, with the males all having commandeered a shell to build their nests. Now that the sand gobies are in their own private space perhaps they’ll breed?
Gobies at War!
So as I mentioned, on that trip to gather seaweed I struck lucky with another rock goby (who I’ve named ‘Rocky 2’). However, the issue I had was where to keep it until I could properly segregate the tank. The best temporary solution I could come up with was to use another breeding net to keep it in until it settled in. Then, after 24 hours I thought it would be a good idea to introduce ‘Rocky 2’ to ‘Rocky’, so I stupidly (as it turned out) put them both in the same breeding net.
A day or two later the separator screen I ordered from Temu arrived (see photos below) and I sectioned off the tank into two. When I scooped out the two rock gobies though, the newcomer was badly beaten up. Its fins were shredded and it had what I assume was a bite mark on its back. It wasn’t in a good way and when I added it to the main tank it was incredibly shy and spent most of its time hiding.
I barely saw it for two days, and when I did it was usually being chased by the other one. Until day three, when it came out to feed and looked much better. The wounds were still there but its body language was much happier and it was feeding well, alongside the other rock goby and the five blennies it now shares a home with. It healed surprisingly quickly (within a week it looked almost back to full health) and things have definitely settled down in there now with the two rock gobies seemingly having established their own territory. An uneasy truce has been established although Rocky 1 is still occasionally showing who is boss.
In truth though I don’t like having the tank sectioned off so I’ll need to make a decision on whether to keep the rock gobies or the sand gobies, as having both isn’t an option.
