Problem introducing new fish

[Clavius78]

I have an old 500 liter tank of just over 10 years old now. (132 gallons) Mixed SPS/LPS/softies -corals and clams are doing great. Current fish inhabitant too. Two of them are Zebrasoma that have been in there from the start. One of those is a Xanthurum that was already in the previous owners tank for over 15 years. So it's 25 years old at least and still looking fine and very active.

The rest of the inhabitants consist of:
- 8 Chromis Viridis
- 2 Pseudochromis Fridmani
- Flame angel (mine is reefsafe)

Just 12 fish, of which 2 are somewhat larger. Not a very crowded tank at all. I constantly need to add nitrate and phosphate, otherwise my corals would perish, so my tanks processes definitely support more inhabitants.

So, here comes my problem: Whenever I try to introduce new fish they disappear within days. This friday I tried to introduce a couple of fire gobies and a green goby. One fire goby swam around for the evening. It even ate immediately. The other fire goby and the green goby went into hiding directly. I could see the fire goby in its hiding place. It looked as if it was in shock. Of course I left them alone to recover. But the next day all new three fish were gone. I haven't seen them since.

And this is not the first time. I've tried to add fish before, with the same result.

To add fish I'm using the same procedure that I've always used: gently insert the fish with the water from the store into a bucket. Put in a dripper that slowly acclimates them to the new water parameters. I leave them there for a few hours. Then I add them to the tank.

And unless I have fish that change character when the lights go off at night, I don't see any aggressiveness towards newcomers whatsoever. They all just focus on me and ignore each other completely.

My water parameters seem fine:
NO3: 1
PO4: 0.01
(I keep those two there artificially. With so many corals and so little fish it's quite easy to reach undetectable levels. Even to the point where corals suffer.)
KH: 8
CA: 420
MG: 1250
Salinity: 1.027

Is there anything you guys can think of that can cause this? What am I doing wrong? Or tell me you safest, full proof, procedure for introducing new fish.

Should I add bigger, less delicate, fish instead? (I'd love to add another Zebrasoma, like a Desjardini, but I'm too afraid it would cause a war with the older two that have been in my tank since forever.)

 

[oldhead]

Sounds more like you have a predator in the tank that you don't know about. Maybe a couple hours after lights out try a black light. Odd that the other fish don't disappear also, unless they know where not to go.

 

[Clavius78]

Sounds more like you have a predator in the tank that you don't know about. Maybe a couple hours after lights out try a black light. Odd that the other fish don't disappear also, unless they know where not to go.

Yes, I ruled out that possibility as my other fish are unaffected. Even if they're very smart, you'd think a predator would be in luck sooner or later.

 

[Flapjack287]

What do you have in terms of anemones? Also do you have a night light for the fish? In my reef we have a very low powered blue light so the fish can direst themselves better at night.

 

[Clavius78]

What do you have in terms of anemones? Also do you have a night light for the fish? In my reef we have a very low powered blue light so the fish can direst themselves better at night.

I've got two red anemones. (Entacmaea quadricolor) I've had those since the start. They're always in the same place.

There is no light whatsoever during the night. Not even from outside street lights, because of our shutters. Pitch black darkness. Wouldn't the natural reefs be equally dark at night?

 

[Megalonyx]

I used to have the same problems and it was from a predator. I had a defensive pistol shrimp nab a few fish while leaving the established ones alone. It may have been because the fish established in the tank were less prone to hiding under the rocks on the sand bed where the shrimp was.

 

[pisanoal]

What salinity are the fish coming from?

A drip acclimation, even over several hours, can be too quick to raise salinity from 1.019 to 1.027. I think general rule is .001 per day of salinity increase. A lot of people get away with more, but sometimes you don't.

Also, where are the fish coming from?

If being shipped, don't drip acclimate. They need to go into at least short term QT that matches salinity if not kept at full reef salinity. Float for temp and add them straight in.

 

[Uncle99]

You say you leave them in a bucket for hours, do you heat this bucket to same exact same temp as your DT.....cause temp differences are the leading cause of fish deaths next to differences in salinity.

Both I place any fish in the DT, the temp and SG must be equal, however I do this in a QT for 30 days, not lost anything to date.

If your going from bag to DT, slowly adjust the SG to match, then float the bag for 30 minutes, then add...

 

[Hal]

Can I suggest that you start using an isolation tank when introducing new fish? I've found that 3 days in an isolation tank in the DT pretty much kills most aggression from the existing fish.

Also, just because you can't see the fish doesn't mean that it is dead. I introduced a flame angel that disappeared within 48 hours. It popped up 3 months later. Seriously, try as I could during those three months, there was no sign of it, not even during feeding. I peered through live rock cracks with a flashlight. Nothing. Then voila!

 

[Clavius78]

Thanks everyone for the suggestions!

The last time, this Friday, salinity between the water from the LFS and my tank were exactly the same. So that wasn't it. But as suggested, the temperature difference could surely be the culprit. The water in the bucket that I used will cool off, as the drip method is not fast enough to equalize the temperature to the tank.

I'm going to invest in one of those floating isolation tanks. And acclimatize new fish in the tank first.

 

[Rallos]

If you're not using a dedicated quarantine tank and just putting the fish from bag to DT I would skip the drip acclimation altogether. Unless the salinity is more than a few points off, the temperature drop (and lack of oxygenation of the water, unless you put a circulation pump in the bucket) from being in a bucket for hours is far worse for the fish. You can get a floating mesh cube to add the fish to inside your DT so they can sort out pecking order issues while being protected. I've done this with all my fish and have never lost one unless it got eaten by another fish.