What's wrong with our GSP?

[AimSOx]

Hello! New to the board so please bear with me!

We have had our GSP Tony for around 14 months, he's been in a 27 gallon tank for approximately 12 months, brackish (was fresh water when we got him but have slowly (over the last year) been increasing salinity), and is the sole occupant, along with some stunning bog wood and a rock sculpture.

He used to swim around a lot, come to the glass to see us, respond to his name, and come to the top for food. We have been plagued by blue-green algae for months, our water is tannin stained from bog wood (though we don't mind this), coupled with the algae everywhere the tank looked awful! Fed-up with cleaning/hoovering twice a week just to stay on top of it, we followed advice and did a total black out for four days. Of course we fed Tone during this time, and he is in the living room so he would have heard us going about our daily routines.

After four days we removed the cover and the algae had all-but gone, the tank looked much better. Tone didn't. Since we did this (coming up two weeks) he has been really sad, staying at the bottom of the tank, always slightly grey, sometimes black and on occasion (though rarely) white bellied. He does seem to be eating - he happily attacked a cockle at the weekend, though not as persistently as usual. He does appear to have lost weight.

One other anomaly; he sometimes throws up, actually vomiting. He did this for the first time earlier in the year, and has done it twice more since his black-out. It's not after eating (it seems rather random) and he does eat a lot of what comes out. Should we be worried?

We are at a loss with what to do - any advice would be welcome, it's awful to see him so sad. This is our first experience with any puffer, and we were misinformed by the fish keeper that he was solely fresh water. We were also not told of his diet - as a household of vegetarians we would have made a different choice if we had known. Yes we should have done more research but you live and learn and we love him regardless!

Levels seem good:
Ammonia - 0
Nitrite - 0
Nitrate - less than 20
ph - 7.5
Salinity - 1.018
Temp - 27/28
Food - cockles, muscles, brine shrimp and krill
Water change - at least 10% weekly added
Filter - Eheim Professional 4+ 350litre

[Pufferpunk]

Your pH is low, because of the bogwood. I'd remove that. What substrate are you using? What else are you feeding?
What do you mean by: "Water change - at least 10% weekly added"?

[AimSOx]

Thanks for getting back to me.

I thought the ideal ph was 7.5-8.5? Would adding coral shells be of any help?

Apologies, that shouldn't say added at the end, just weekly water change!

We removed all the old cockle shells before the black out, could that have had an impact?

[Pufferpunk]

7.5-8.5 is a HUGE pH difference. A steady level of 8 is best.
50% weekly WC are recommended.
At 1.018, you're practically SW. I suggest raising it slightly more & add live rock & a protein skimmer.

[AimSOx]

Thanks, Pufferpunk.

We added some shells last night to start bring the pH up, and will increase salinity further - we don't have room for an external protein skinner (the tank fits snuggly into the alcove), do you have any recommendations for slimline ones?

We'll also get shopping for some live rock, though looking online it looks similar to what we know as lava rock - are they one and the same? We have some of that we could put in..

What do you think to the algae? It's starting to bloom again now so I guess we just have to put up with it, as Tony hated the black out so much. Funny, the water levels were the same before and after, he's just gone all sulky and sad!

[Pufferpunk]

I am referring to switching this tank over to a completely marine system. Live rock is nothing like lava rock. I was able to hang a protein skimmer on the side of one of my tanks. By using live rock, live sand & removing your FW filtration, it should help with the algae.

[AimSOx]

Thanks, Pufferpunk. So are you suggesting removing our Eheim filter all together? I have been looking at protein skimmers today and there are a few slimline options that we could hang on the tank.

I've also looked more into live rock - thank you for clarifying the difference there! Live sand is new, so I will have a look at that, too.

He had gone of his food last night but has taken a shrimp this morning. It really is a worry.

[Pufferpunk]

Yes, after you have a solid, established marine system, the Eheim is nothing more than a "nitrate factory". Sand becomes "live" after being in a tank with live rock for a while.