Most everything I've read about dartfish seem to concur that they are peaceful fish that will fight with others of their own kind. However, I've had slightly different experience (so far). I initially purchased a Firefish (Nemateleotris magnifica). A few months later I found a nice big Purple Firefish (Nemateleotris decora). The decora then proceeded to take over the tank and harass the magnifica until it was missing half of its tail fin and relagated to less than one half of the 4' tank. This aggression didn't surprise me much at all. However, a month or two later I added another much smaller decora. I was worried that the larger decora would harass the smaller as well, but quite the opposite has occured. The two decora hang out like they've been best friends forever and the poor magnifica has been relegated to less than 1/3 of the tank. I was almost certain that there would be some degree of aggression between the two decora given their size difference, tank introduction differences and what not, but I stand nearly stunned at the outcome. I plan to add two more magnifica to see how that changes the dynamic. I'm hoping a three against two situation will even the territory out. I may be asking for trouble adding that many firefish, but I really want to know how it turns out. Any thoughts/predictions?

Hey Rychek,

I've broken a few similar rules like this as well and had some positive results that I didn't really expect. I think it is hard to predict what you will see in the future to some extent because there are a lot of variables like how much rockwork you have and I've even noticed some difference with my FW tank when I add fish with the lights on or off. But, I probably wouldn't say that everyone who adds fish with the lights off will be guaranteed that everyone will live in harmony. I also think that finding exceptions to the "rule" gets a bit easier when you know what you are doing so this might account for some of your surprising "luck".

I figured keeping each type of firefish in a small group would mitigate aggression globaly (tankily?). I'll find out in a day or two. I'm not sure having the light on or off made any difference. Although, the fact that all of my fish were "sleeping" for the night may have had some impact.

I figured keeping each type of firefish in a small group would mitigate aggression globaly (tankily?).

Does "tankily" qualify as a "Bush-ism"?





To be honest, I've only kept firefish for a few weeks as a favor to a friend and they were in a q-tank so I've never really seen how they are around other fish. I've always been under the impression that males and females are ok together and if the tank is big enough, it might be ok to have a couple pairs. Is gender at play with your fish at all?

I don't know if gender is playing a part in my tank or not. I don't know how to tell the males from the females yet. It's on my list of things to research today.

Edit:
I was reading over on the MOFIB board and this what they have to say about Dartfish in their breeding sub-forum

"
3.2 – Sexual organization:
Pairs - probably monogamous pairs. Many of the species in this group are routinely found as pairs in the wild. In Nemateleotris, juveniles may be found in groups, but aggression sets in upon maturity.

3.3 – Sexing:
There does not appear to be any reliable means of outwardly sexing a dartfish. Pairs appear to be sexually
monomorphic
and sexually monochromatic. Observations of intraspecific behavior / interaction is most often the "key" to identifying a pair. Within an actively reproducing pair, you may be able to identify the sexes during the pre-spawning period when the female "ripens" and becomes swollen with eggs." --emphsis mine.

I'm thinking my purples are getting along because one is a juvenile (I'm hoping they could become a pair, but I don't want to get my hopes up too high). I'm also thinking that the magnifica and the decora don't get along because they both appear to be adults. Perhaps getting two more magnifica isn't such a good idea....

I'm not sure how it happened, but my new purple firefish is dead. He spent a day or so on the bottom of the tank with what looked like a broken back. He looked as if a larger fish had tried to eat him tail first and failed (tail, dorsal and anal fins shredded, back/ sides discolored). The only thins is, I don't have any fish that big.

Sorry to hear that Rychek. I assume it looked fine when you let it out of the bag, right? Any chance that it might have gotten into a fight with a pump or something?

I doubt the larger Purple was the problem. They seemed to hang right next to each other out all day long. I think he might have had a close encounter of the Koralia kind. I don't think any of my other fish would be capable of doing the kind of physical damage he seemed to have.

Well that stinks. I've had some problems with pumps/intakes in my tanks so I've always wondered if the Koralias might pose some risks but since I haven't heard/read anyone who might have had a problem until, I figure they must be pretty safe. Perhaps your new fish settled in away from your rock at night and got a little too close? As I mentioned before, I've 'baby-sat' a couple firefish for a short time and one of them would always be huddled in one of the front corners of my tank for the first few days.


I know the monetary loss can be unmotivating, but do you plan on finding a replacement for the fish you lost?

At this point I think I'm done with little firefish. The two I've got are fairly large (for dartfish at least) and I almost feel like their survival has been a fluke. I've lost enough money on them for now. I think my next fish will be something that will eat the macro that has made its way into my display from my fuge. I'd like to get a tang, but with a four foot tank my options are limited.