Development of a Danio Fry  9/5/08
Dear WWM Crew,
Can you please tell me how long it takes for a Danio fry to develop (weeks/months)? Thanks for your help in advance. Jean
<Hi Jean. It should take about 3-4 months for the fry to develop into fish big enough (half adult size) to either return to the aquarium or sell on. They are sexually mature within 6 months; males generally a lot sooner than that. Growth is fastest during the first few weeks, but this depends on them getting lots of meals (ideally, as many as 6 per day) and large scale water changes so that nitrate in the water is minimised. Water temperature also makes a huge difference. Cheers, Neale.>

High pH, Fighting Danios
Hi guys. You have the greatest website! I got my first tank two weeks ago. It is a ten gallon freshwater community tank, several plastic plants, 50 watts heater, two thermometers one internal and one external, one fake rock with 3 holes on it, one undergravel filter, two inch deep gravel strata (rounded and more or less pea sized), one aqua-tech outside power filter, one small sponge filter. The pH of our tap water is about 7.4 to 7.6. I added water conditioner (Tetra Aqua Safe), Stress Zyme, five teaspoons of salt for freshwater aquarium. At the beginning the water got a little cloudy. I waited one week and added 3 Zebra Danios Next day I added one ounce of Bio-Spira freshwater bacteria from Marineland. The water became clear again within 24 hours. The Danios (one small male, one small female and a larger older individual whose gender is a mystery to me) were fine. They were exploring and racing around. Then the two smaller Danios began to dance in circles at the bottom of the aquarium. The older individual took possession of the upper and middle part of the aquarium and began to chase and bump-fight the small male while the small female was hidden in the plants. Within 48 hours the small male stopped racing and eating and died. I examined the body. There were no signs of disease or injury. The older individual still chases the small female every time they meet. The small female is fine but she is confined to a corner of the aquarium that is covered in plants most of the time. She ventures out often, but she goes back when the larger Danio chases her. When I feed the fish, I feed them very little food, twice or once a day. I try to feed them the minimum amount of food possible. I underfeed them because they are too busy fighting each other to eat all of it. Although the Danios come immediately to the food, they promptly begging to fight and some flakes end up sinking and the fish remain hungry. I worry about the food sinking. My last pH reading is in the range of 7.6 to 8. My ammonia reading is 0. My nitrite reading is 0.2. I have several questions:
What could have happened to the small male Zebra Danio?
<<Aggression, high ammonia, nitrites. What did your ammonia test at last week? Must have been some, there has to be ammonia for it to be converted into nitrite. Do you have nitrates yet? You should be testing this tank everyday.>>
What is it with the large Zebra Danio (I was told they are peaceful fish)?
<<They are not. And a toxic tank will not make them any nicer, either...>>
Could the small female Zebra Danio be hurt by constant harassment?
<<Certainly>>
Is it a good idea to add other fish to the tank?
<<No.>>
If so is this list a good list: one male Beta, two more Zebra Danios, two female Guppies and two small Cory Cats? Are this fish too many (taking into account all my filters and that I am willing to do a 25% water change weekly and a mayor water change monthly)? Would they take my pH as it is? How can I modify this list to avoid disaster?
<<Do NOT add any fish now. Your tank is still cycling. Hence the high pH, etc. And certainly don't add all of these at one time! And definitely avoid putting guppies and a Betta into a tank with Danios. Disaster awaits if you do.>>
Until now I have resisted the impulse of applying pH-lowering product to my tank but What can I do with my pH (7.6 to 8.0)? Should I make a 25% water change now (taking into account that the food keeps sinking because of the fighting of my Danios)?
<<As I said, your pH is high because the tank is CYCLING. It will stabilize in a month or so. Have PATIENCE, please. Do not mess with your pH, you will not be helping your fish if you do. The pH will end up all over the place, and your fish will end up dead from a combination of pH shock, nitrite poisoning, and stress..>>
Finally, If Bio-Spira is so amazing, why are some dealers against it? Thank you for your help.
<<I personally like Bio-Spira, it's an excellent product when it's being used properly. However, results will differ from tank to tank. Dealers simply don't like it when people with no experience try to cycle with it and end up with dead fish, as in your case. Please do some reading, buy yourself some ammonia, nitrite, and nitrate test kits, and be PATIENT. Test your water regularly, do water changes when readings become high, and do NOT add fish until the tank has NO ammonia and NO nitrites left. Keep two small fish in the tank during cycling. TWO! not more! Keeping a written record of your test results will help. :) -Gwen>>

Danio Swimming into HOB Filter - 3/16/2006
Hey Crew, here is a new one...to me, anyways. I have three zebra Danios in a 10 gallon cycled quarantine tank. I am seeing some very odd behaviour from one (or perhaps two) of these fishes. Twice in the past 24 hrs, one of the Danios has found his way up into my hang-on-the-back power filter. I say "one" of them, but I am not sure...it could have been two different fish who did this. On both occasions, I have found the fish swimming around in the confines of the filter's media chamber, unharmed. Does this behaviour signify anything, other than the antics of hyperactive fish?
<<It is likely out of curiosity, but could be a sign of something else.  How are your water parameters? It could be due to aggression from the other fish as well.  Keep an eye on them, just in case.>>
Is there any device I can employ to stop them swimming up into the filter?
<<If there is no screen in the intake, try some filter floss, or a bit of screening of some kind to fashion your own.>>
It is rather alarming to me that they are doing this, not to mention risky to the fish when I have to retrieve them.
<<Risky in general.  Do cover the intake!>>
Any help you can offer is appreciated.
<<Glad to help. Lisa>>
JM

Minnow behaviour & health    10/3/06
Hi
<Hello there Charlotte>
I have four pairs of minnows (2 zebra Danios, 2 coldwater, 2 long fin and 2 yellow ones: apologies for the lack of description by proper name but I can't remember).
<Perhaps a small journal you can keep...>
  They all get along quite happily with four fancy goldfish and a coldwater Plec and all seem in general good health, having joined the goldfish approx 6 months' ago.
On Sunday, I purchased 3 very tiny fantails (one smaller than the zebra minnows!) and all seem well.  Today I have noticed that the yellow and long-fin minnows seem to be displaying to each other by opening their fins wide and synchronized swimming! I have been trawling the internet and my books but none give any indication as to what this behaviour means.
<Perhaps reproductive behavior... maybe just dominance displays>
Is it possible that it's due to the slightly reduced territory now there are 3 new fantails (albeit very small ones) or is it a breeding thing (one of the yellow ones looks a bit portly)?
<How large is this system?>
As a secondary point, on reading various articles relating to minnows I noticed in one of yours reference is made to a bent spine indicating TB infection.
<One possible cause of several... covered on WWM.>
This concerns me as one minnow has a very bent spine.  He's always looked like this, has grown well since purchase, as have all the other fish.  As mentioned above, all of the fish in the tank seem in general good health and water quality is fine.  Should I be concerned about TB or do I just have a minnow with a wonky back?
Your comments would be greatly appreciated.
Many thanks,
Charlotte
<Please read here: http://www.wetwebmedia.com/FWSubWebIndex/gldfshsystems.htm
You may need more room, less fish livestock. Bob Fenner>