Violet Goby Observation   11/5/11
Dear WetWebMedia Crew,
Greetings. This is my first time writing to you, so please let me begin by thanking you for this wonderful resource. I have spent many hours reading through your pages. WetWebMedia has not only helped me answer questions, it has also inspired me to select many of the specimens that I currently keep. Thank you!
<Thanks for the kind words.>
I am writing with an observation that I have made regarding my dragon goby (Gobioides broussonetti). First, a little history... I purchased it about four months ago from a freshwater tank at a chain store. I had planned on the purchase, so I had already set-up and cycled a 30 gallon freshwater tank which housed a school of guppies. Upon purchase, I added the dragon goby to the freshwater tank and after 24 hours, I began converting the tank to brackish by doing 20% water changes every 2 days. With each partial water change, I removed 6 gallons of water from the tank and added 6 gallons of pretreated/dechlorinated (using AquaSafe), premixed brackish water with a specific gravity of 1.005 (using approximately 2 tablespoons per gallon of Instant Ocean marine salt). I continued doing this every 2 days until the specific gravity of the tank measured 1.005.
<Sounds good. These fish are very adaptable, but in completely freshwater conditions they rarely do well indefinitely. Even slightly brackish water makes all the difference. In the wild they're often exposed to fully marine conditions.>
Within 3 days of bringing the dragon goby home, he developed a very bad case of Ich. I raised the temperature from 72 degrees Fahrenheit to 82 degrees Fahrenheit and continued to increase the salinity as described above. During this time the dragon goby was eating, hiding, digging, and exploring, despite the white spots. Within a week, his symptoms disappeared, but I waited another week before gradually lowering the temperature back down to 72 degrees Fahrenheit. The guppies did not appear to show any symptoms of Ich during this time.
<Precisely so. The heat and salt kill off the free-living stages, so the infected Violet Gobies weren't able to infect your Guppies. On the other hand, it takes a few days for the parasitic stages to complete their life cycle, and so it will be some days, perhaps a week, before the symptoms disappear from your infected Violet Gobies.>
After I had him for about a month and the specific gravity of the tank was now stable at 1.005, I slowly began adding more specimens over the next eight weeks. I added one knight goby (Stigmatogobius sadanundio),
<A good companion for these, but predatory towards small fish and shrimps.>
five bumblebee gobies (Brachygobius xanthozona),
<Almost certainly not this species. But in any case, Bumblebee Gobies are frequently eaten by Knight Gobies, so not an ideal purchase!>
two flounders (Trinectes maculatus),
<A subtropical species, and difficult to feed when kept with other bottom-feeders. Bumblebee Gobies would be acceptable at lowish temperatures, say, 24 C/75 F, as would hardy or "feeder" Guppies, but Violet Gobies are a questionable choice here. The problem with soles and flounders is that they often starve to death in aquaria.>
ghost shrimp, and pond snails. The knight goby promptly ate all of the guppies except for the two largest females.
<Ah, yes.>
They are still in the tank, but the knight goby promptly eats their offspring whenever they arrive.
<Yes.>
Now that the tank is fully (!) stocked and stabilized and I have had time to observe everyone's behavior, I do wish that I had not added the knight goby to this system.
<Actually quite a good companion for the Violet Gobies, perhaps with assorted Sailfin Mollies for colour. All will get along well, eating different things or at different times, and the Knight Goby will of course eat unwanted Molly fry.>
I have since purchased a 75 gallon tank (with knowledge that the dragon goby will soon outgrow the 30 gallon), and plan to move the dragon goby, bumblebee gobies, and flounders to that tank in three months -after it has matured. Then I will keep the 30 gallon as a species-only tank for the knight goby (and will perhaps add others of his kind to it).
<I wouldn't do this; I'd keep this tank for the BBGs and the Flounders. Plain sand, a few shells, slightly brackish water, low to middling temperature'¦ perfect! You could rescue a few Molly fry for this tank as/when, if you feel the need to grow on some adults for the bigger tank. Or else add something else quirky, like Wrestling Halfbeaks or Humpbacked Limia.>
Although I have grown fond of him, the knight goby seems much too feisty and ornery for this otherwise peaceful community.
<Yes, they are territorial. Males perhaps more so than females.>
He doesn't bother any other specimens except the guppies, but he's always racing around looking for more guppies and when I feed him foods that he's not fond of, he picks up sand in his mouth and spits it at the glass towards me. (I'm not kidding!)
<As I mentioned, very much more predatory than many expect.>
For what it's worth, I have kept various freshwater tanks and two ponds for many years. This is my first brackish tank. The current tank parameters are as follows: ammonia=0, nitrites=0, nitrates=less than 20ppm, pH=7.0, SG=1.005; maintenance schedule=20% water change weekly with gravel vac and filter cartridge rinse (replace as necessary), algae scrub as necessary. The filter is a Marineland HOB rated for 30-60 gallons, and there is an 8-inch bubble curtain on one wall of the tank. There is a florescent light on the tank which is on for 10 hours a day (dimmed by some floating plants). The tank is planted and includes Anacharis, hornwort, Aponogeton, onion plant, water sprite, java moss, java fern, and some hair algae. For decor, there are various caves, tubes, rocks, shells, etc. for the critters to hide in, with an open space in the middle. There is also one skinny piece of driftwood. The substrate is a coarse sand (I have chosen a finer sand for the upcoming 75 gallon). The only other thing I should mention is that I add 3 drops of Kent's marine iodine to the tank once a week with partial water changes (for the shrimp).
<All sounds good.>
Finally, onto my observation regarding the dragon goby. It is active and eats well. It has grown quite a bit in length and girth since I got it. It accepts any foods that it finds and I feed it a very varied diet of live, frozen, freeze dried, processed, and fresh/blanched foods (I've even seen it chewing on a piece of blanched Brussels sprout!)
<Yes: they do eat some plant material, esp. algae; their teeth are apparently adapted for scraping algae from rocks. So alongside gulping plankton like whales and sifting sand like starfish, they can scrape at algae like catfish! What wonderful animals they are.>
It acts healthy and looks healthy... but here's the thing - every morning when I turn the light on, it comes out of its tube (charcoal colored pvc pipe) and it's pink! It's not a cloudy-slime-coat-grayish-pink, but a clear-I've-gone-albino-overnight-pink.
<It is not unusual for fish to change colour at night.>
It hunts around for food a bit, then goes back into its tube, and when it comes out again - it's gray (usually within a half hour). It stays gray all day and into the night (after lights-out), but the next morning -pink! I have not been able to observe the color-change in action so I don't know if it happens quickly or little-by-little. Although, some mornings, it's pink with tinges of gray around the mouth and spine area and on the very tip of each scale (color change in-action?).
Is this normal?
<Probably, yes.>
Has this been observed before?
<Not by me.>
Should I be concerned?
<No, not if he's otherwise healthy, hungry and growing well.>
I've attached four pictures. The first two (goby-pink.jpg and goby-pink1.jpg) were just after I turned the lights on and it came out. The second two (goby-violet.jpg and goby-violet1.jpg) were taken one hour later on the same day. My best guess is that the lack of light overnight triggers a halt in melanin production (?) which resumes later, once exposure to light has been resumed (or something like that...)? Any guesses?
<Your guess is probably close to the truth. Fish "think" their colouration, and almost all of them can change their colours to some degree. At night they may alter their colours, perhaps to be less noticeable, or else because they can't see what colours they need to be. Neons are the classic examples of this.>
Thank you for your time. And thank you in advance for any insight you may have. Sorry if this was too lengthy, but I wanted to be sure I covered everything. If you have any further questions, please feel free to ask.
Sincerely,
Val H
P.S. I also have some other pictures of assorted (freshwater) aquarium oddities that may make useful additions to some of your existing pages. If you would be interested in these, please let me know and I will send them along.
<I do think you might enjoy sharing these over at the WWM Forum, here:
http://wetwebmediaforum.com/
For one thing, you'll be able to get some feedback from forum members, which is always fun! Cheers, Neale.>

Re: Violet Goby Observation  -- 11/08/11
Dear Neale,
Thank you for your quick reply and for sharing your observations
<<Glad to help.>>
Re: bumblebee gobies (Brachygobius xanthozona),
<Almost certainly not this species. But in any case, Bumblebee Gobies are frequently eaten by Knight Gobies, so not an ideal purchase!>
Yikes! ...and double-yikes to my misidentification!
<<Quite so.>>
Re: two flounders (Trinectes maculatus),
<A subtropical species, and difficult to feed when kept with other bottom-feeders. Bumblebee Gobies would be acceptable at lowish temperatures, say, 24 C/75 F, as would hardy or "feeder" Guppies, but Violet Gobies are a questionable choice here. The problem with soles and flounders is that they often starve to death in aquaria.>
I do have to "spot feed" the flounders using a turkey baster. I have observed them eating frozen bloodworms, frozen brine shrimp, and live blackworms. I've also seen them scuffling with live scuds (Gammarus shrimp) but I wasn't able to determine whether they were eaten or not.
<<If feeding, and looking plump, then all is well. But do be aware of the potential problems re: water temperature, adequate feeding.>>
Re: <I wouldn't do this; I'd keep this tank for the BBGs and the Flounders. Plain sand, a few shells, slightly brackish water, low to middling temperature'¦ perfect! You could rescue a few Molly fry for this tank as/when, if you feel the need to grow on some adults for the bigger tank. Or else add something else quirky, like Wrestling Halfbeaks or Humpbacked Limia.>
Thank you for your advice regarding the tank upgrade. I will reconsider my plan accordingly.
<<Cool.>>
Re: <Your guess is probably close to the truth. Fish "think" their colouration, and almost all of them can change their colours to some degree. At night they may alter their colours, perhaps to be less noticeable, or else because they can't see what colours they need to be. Neons are the classic examples of this.>
I'm glad you confirmed my suspicions that the dragon goby is probably okay, just changing color with the day/night cycle.
<<Also cool.>>
Re: <I do think you might enjoy sharing these over at the WWM Forum, here:
http://wetwebmediaforum.com/
For one thing, you'll be able to get some feedback from forum members, which is always fun! Cheers, Neale.>
Oh, yes! I did register for the forum, but haven't had a chance to post yet. I'll try to stop by and post sometime this week. Thanks again, Neale. Your advice is greatly appreciated!
<<Do hope you enjoy the forum.>>
Sincerely,
Val
<<Most welcome, Neale.>>