Danio Fry Dying

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bsantucci

Aquarium Advice Activist
Joined
Aug 14, 2013
Messages
184
Hi all,

I had some zebra danio fry, about 12 total now for 2 months or so and they were doing great and growing. Yesterday two of them were laying on the bottom of the tank and breathing heavy and they were dead this morning. I see another on the bottom now doing the same thing. I have no idea what is wrong with them. I have 7 cory fry in there as well and they are completely fine.

ammonia is 0, nitrites are 0, and nitrates are about 5ppm. They don't look ill at all. Any ideas?
 
Hello b...

Most, if not all tank problems can be taken care of with large, weekly water changes and putting in a variety of plants. The water changes remove most of the toxins produced from the dissolved fish waste and the plants use the remaining wastes for food. The tank water stays safe for the fish.

I'd recommend changing out half the tank water every week and replace it with pure, treated tap water. Floating plants like Anacharis and Pennywort are two of the best for natural water filtration.

I'd also add a bit of standard aquarium salt to the replacement water. A teaspoon for every 5 gallons of new water is sufficient to keep your fish healthy and the small amount won't bother your aquatic plants.

Nutrition is almost as important. Feed mostly frozen, a little freeze dried and minced garlic for vitamins and a natural antibotic and very, very little flaked (typically high in non essential additives). Feed just a bit about every other day or so.

Follow these suggestions for the life of the tank and see if this doesn't improve the health of your fish.

B
 
Thanks for the reply. I do water changes quite often so the water quality isn't the issue. I also have anacharis floating already too. I feed frozen brine as well as live vinegar eels so I really doubt it is diet.

That's why I'm puzzled with this die off. Any other ideas?
 
Our Tank

Thanks for the reply. I do water changes quite often so the water quality isn't the issue. I also have anacharis floating already too. I feed frozen brine as well as live vinegar eels so I really doubt it is diet.

That's why I'm puzzled with this die off. Any other ideas?

Hello again b...

Okay. We can look at the filtration. A standard filtration system will turn over roughly 4 times the water volume of your tank every hour. With large, weekly water changes, this is all that's needed to get a sufficient amount of oxygen into the tank water and to allow carbon dioxide to escape (gas exchange).

If the filter system isn't creating enough surface movement, then your fish could be short on oxygen.

B
 
Hello again b...

Okay. We can look at the filtration. A standard filtration system will turn over roughly 4 times the water volume of your tank every hour. With large, weekly water changes, this is all that's needed to get a sufficient amount of oxygen into the tank water and to allow carbon dioxide to escape (gas exchange).

If the filter system isn't creating enough surface movement, then your fish could be short on oxygen.

B

Filtration again, should not be a problem. This is a ten gallon tank and I'm running a seeded sponge filter rated up to 40 gallons. It has the pipe that runs to the surface so there is plenty of surface agitation.

Keep the ideas coming cause I'm sure out of them.
 
Not sure if you do or not...but break up some of the food you feed your fish into tiny almost barely visible particles for the fry. My fry (platy and guppy) won't eat unless it's well broken up.

I've read that all fry is difficult to keep sometimes and grow weak and die before becoming juveniles.
 
Not sure if you do or not...but break up some of the food you feed your fish into tiny almost barely visible particles for the fry. My fry (platy and guppy) won't eat unless it's well broken up.

I've read that all fry is difficult to keep sometimes and grow weak and die before becoming juveniles.

Thanks Hunnelips,
I don't think that is the problem either to be honest. I'm feeding them vinegar eels which are SUPER small, like 1/8th an inch small and are free swimming. Their protein is definitely plenty.

I'm wondering if it was just a genetically bad batch. It's not the end of the world, I was going to trade these for some rock from my LFS, but I just want to get the the bottom of the deaths. Especially since the cory fry is fine.
 
Hello b...

The water chemistry in small tanks can change very quickly, because there isn't enough water to dilute even small mistakes in tank management. Have you considered moving your fish to a larger tank? I tried without much success to keep small tanks. I came to the conclusion, I couldn't change enough water often enough to maintain a stable water chemistry. It wasn't until I moved everything to a 30 gallon tank, that the health of my fish started to improve.

Now, I keep several 55 gallons tanks and they're much easier to maintain than the small ones.

B
 
This is just a grow out tank. I'm fairly certain my rams or apistos would eat them at this size plus I was giving them to my lfs for store credit. I had no intention of keeping them.

I do daily water changes so I really don't think it is a water problem.

I do agree larger tanks are much easier. My 46 gallon basically runs itself aside from the weekly water change.
 
Are those brine shrimp or baby brine shrimp you are using ? Fry need a high level of fats to develop well, and BBS have more of those. Once they are past about 24 hours old, they don't have nearly as much to offer nutritionally, especially to fry. Vinegar eels are also not good fat sources.

If you can, culture some microworms, and/or banana worms. Both are high in fat, and make a great treat for adult fish, but are an excellent fry food, because of the fat content. Low fat levels or inadequate amounts of the right fats can have quite an impact on survival of fry.

Micro worms are easy to culture. Oatmeal substrate and dry bakers yeast as food are all they need. Banana worms are the smaller, half the size of microworms, but both are very tiny. They live at least four days in water, if fry will bottom feed, you can put in enough for a day or two and not worry about them dying and the fry just pick them up. I raise all my Endler fry on them and they're doing great. Good growth, no problems.

Another possible choice is Dero worms. They live in water, so dying off is not an issue. Quite long, but very skinny, so good for fry once they are past the first week or so. Said to be easy to culture, I just can't get them here to try out, at least, not yet. But you can get them in the States. Very popular with Guppy breeders currently, replacing BBS and BS both, as the brine shrimp are getting more expensive and hatch rates are not always great. Dero worms and live moina [ daphnia relative ] are the foods of choice now for many breeders and commercial operations as well.
 
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