Questions about Cory Fry/Please help!

[Corydoras82]

Hello! I am new to this forum so I hope I am posting this in the right spot. I have some questions regarding my pepper cory fry. This is my first time successfully raising any. The first couple go rounds, didn't go so well, as I am just learning. If anybody could please help answer my questions, I would greatly appreciate it!

Here is some background before I ask some questions:

I have my Pepper Cory fry in a 12 gallon plastic tub at the moment. They were in a much smaller tub before that but I was losing many of them to bacterial infection because I did not have any substrate and they were laying in the bio film on the bottom of the tank. I have a thin layer of aquarium sand at the bottom, a sponge filter on opposite sides of the tank (one of them has an air pump attached). I must have about 100 hatched Cory fry. My mama Cory was laying eggs like crazy. January 5th the first batch of eggs started hatching. She kept laying eggs about every 5 days, maybe around 50 eggs at a time. There are 9 different batches of eggs that hatched so I have 9 groups of different aged Cory's. The oldest ones being a little over 1 month old and the youngest ones just a few days old.

Questions:

*I am losing a few of my oldest fry every few days. I can't understand why. It's like once they reach a month old, they start dying off. They will float at the surface of the water, usually upside down, and they have very big stomachs that look silver and shiny? Is that swim bladder? If so, what can I do about it?

*I have sand substrate since I learned the hard way about the biofilm on the bottom of a bare tank. Should I be wiping off the sides of the tub when I do water changes? It has a film on it but some of them like to swim around the sides and seem like they might be eating off it?

*I have noticed some variations in some of the fry. Some are dark colored and active and seem to be doing quite well as far as I can tell, but others are so pale I can hardly see them. The pale ones are not very active. I have also still been losing a small amount here and there due to what I assume is bacterial infection? They are white and covered with a bit of fungus like the eggs tend to get on them. Are the pale ones on their way to dying of bacterial infection or might they actually be ok? I thought I read somewhere that they can camouflage themselves? Might that be the case?

* I recently tested the tank and the nirtite and nitrate levels were not good. I change the water and clean the substrate with a turkey baster 1 to 2 times a day. How can I remedy the nitrite/nitrate situation besides just doing water changes? Is it safe to add beneficial bacteria to the fry tank? The brand I have is called Seed I believe.

*Am I missing anything in my fry tank? Would adding live plants be beneficial?

* Is it too early to add my largest fry, which are a little over a month old, to the parent tank? I would like to before I lose anymore of the bigger ones to swim bladder or bacterial infection. I am just not sure if it would be too stressful at that age, to add them to a different tank.

*Like I mentioned, I have probably about 100 fry at the moment. I am worried about overcrowding. They are in a 12 gallon and all have plenty of space but they grow so quick and I worry about the overcrowding. Have I way surpassed the amount of fry that should be in a 12 gallon tank?

*I would like to add more sand to the tank, as I can't help but suck some up each time I clean the tank. Is it ok to put new sand over old sand?

*Any advice on the diet the fry should need? I am currently feeding them Micron nature fry food. Since there are different aged Cory's I also add something else, usually an algea wafer, crushed up Tropical flakes, Aquatic Frog and Tadpole Food (my adult Cory's love them), or crushed up Baby Shrimp. I can't tell if they are eating the tadpole food but I think they are. They are interested in the algea wafers when I first put them in but they don't seem to eat much of it overall. They didn't seem to care for the crushed up baby shrimp. I feed them a couple times a day. The micron fry food is green and it makes the water look awful. Can someone please suggest a good diet I can provide for them that would meet all their needs?

 

[ghyti]

I am sure others will chime in, but here is my opinion. If there is any NitrIte at all, that is your problem. Get a cycled sponge filter in the tank also an air stone to provide surface agitation. I always keep my baby cories in bare bottom tanks so I don't think the bottom biofilm is the problem. Put some plant material in there, java moss, green hair algae, leaf cuttings etc. That will give them some infusoria to eat. I have found the best diet for the little ones to be live micro worms. Newly hatched baby brine shrimp work too. Again, nitrite is your problem. get the tank cycled and get rid of the nitrite. in the meantime do large daily water changes (50-75%) to keep the nitrite down.

 

[DoubleDutch]

I think daily large waterchanges are key here.

Corys and certainly fry need protein.
Algaewafers, flake food don't have much nutritional value.

Microworms are super food for the first time, crushed shrimppellets are better.
Also be aware dry food can be an issue when eaten dry and then expand inside the fry. So soaking those before feeding is a good idea

 

[Byron]

I will add a couple of things I see. First, does this "tank" the fry are in have a filter? I saw a 12g tub with daily water changes mentioned, but it is important to have some sort of "filtration" involving water movement. A single sponge filter connected to an air pump would suffice.

Sand substrate is crucial as you have found out, so that is good. The biofilm which forms on all surfaces covered by water will host microscopic food, so there is a benefit to the biofilm on the sides of the tank/tub, do not remove this. The biofilm that can form on the bare bottom of the tank/tub is a very different thing, and seriously dangerous to fry. This surface is where the uneaten food and fish excrement lands, and without a substrate of sand there is no place for the beneficial waste-eating bacteria and the accumulation of all this "nasty" stuff can seriously harm fry. Ian Fuller says it is next to impossible to keep a bare bottom clean enough for cories. A layer of sand solves this problem.

As for food, dried leaves are just about the best for fry of any fish, and cories will readily graze the leaves for infusoria. Leaves of hardwood trees are generally safe (oak, maple, beech), or you can buy almond leaves in some fish stores. Put a couple in the fry tank, and the leaves will float until they become waterlogged when they will sink. As the leaves decompose, infusoria multiply and this is "the" first food of any fish fry. Studies have shown that dried leaves added to a fry tank will allow the fry to develop much faster, so there is a lot of benefit here. And some say the leaves have good bacterial properties too.

 

[Corydoras82]

I think daily large waterchanges are key here.

Corys and certainly fry need protein.
Algaewafers, flake food don't have much nutritional value.

Microworms are super food for the first time, crushed shrimppellets are better.
Also be aware dry food can be an issue when eaten dry and then expand inside the fry. So soaking those before feeding is a good idea

Thanks for the tip about the dry food expanding if not soaked first. That is most likely why some fry float at the top upside down with huge bellies. I will correct that and hope it fixes that issue. Thanks again!

 

[Corydoras82]

I am sure others will chime in, but here is my opinion. If there is any NitrIte at all, that is your problem. Get a cycled sponge filter in the tank also an air stone to provide surface agitation. I always keep my baby cories in bare bottom tanks so I don't think the bottom biofilm is the problem. Put some plant material in there, java moss, green hair algae, leaf cuttings etc. That will give them some infusoria to eat. I have found the best diet for the little ones to be live micro worms. Newly hatched baby brine shrimp work too. Again, nitrite is your problem. get the tank cycled and get rid of the nitrite. in the meantime do large daily water changes (50-75%) to keep the nitrite down.

Thanks for your response! I will try increasing my water changes, just didn't want to risk stressing them out too much, as when I was doing more frequent water changes, I felt like I was losing more fry than usual. I think I have no choice though, what with the nitrite levels.

Would it be ok to take a live plant from the parent tank and add it to the fry tank?

Do you think it would be ok to add live bacteria to the fry tank?

 

[Corydoras82]

I will add a couple of things I see. First, does this "tank" the fry are in have a filter? I saw a 12g tub with daily water changes mentioned, but it is important to have some sort of "filtration" involving water movement. A single sponge filter connected to an air pump would suffice.

Sand substrate is crucial as you have found out, so that is good. The biofilm which forms on all surfaces covered by water will host microscopic food, so there is a benefit to the biofilm on the sides of the tank/tub, do not remove this. The biofilm that can form on the bare bottom of the tank/tub is a very different thing, and seriously dangerous to fry. This surface is where the uneaten food and fish excrement lands, and without a substrate of sand there is no place for the beneficial waste-eating bacteria and the accumulation of all this "nasty" stuff can seriously harm fry. Ian Fuller says it is next to impossible to keep a bare bottom clean enough for cories. A layer of sand solves this problem.

As for food, dried leaves are just about the best for fry of any fish, and cories will readily graze the leaves for infusoria. Leaves of hardwood trees are generally safe (oak, maple, beech), or you can buy almond leaves in some fish stores. Put a couple in the fry tank, and the leaves will float until they become waterlogged when they will sink. As the leaves decompose, infusoria multiply and this is "the" first food of any fish fry. Studies have shown that dried leaves added to a fry tank will allow the fry to develop much faster, so there is a lot of benefit here. And some say the leaves have good bacterial properties too.

Yes, it has two sponge filters in fact. One on each side of the tub. One has an air pump attached to it.

Do you think it is ok to add new sand on top of old sand? I have been losing more and more of my sand whenever I suck up old food with a turkey baster.

Thanks so much for the advice on their diet. I am definitely going to try some of those out. I have heard of the almond leaves before and my local pet shop sells some, I just didn't realize the benefits it provided. I will give it a shot, thanks again!

 

[Corydoras82]

I am sure others will chime in, but here is my opinion. If there is any NitrIte at all, that is your problem. Get a cycled sponge filter in the tank also an air stone to provide surface agitation. I always keep my baby cories in bare bottom tanks so I don't think the bottom biofilm is the problem. Put some plant material in there, java moss, green hair algae, leaf cuttings etc. That will give them some infusoria to eat. I have found the best diet for the little ones to be live micro worms. Newly hatched baby brine shrimp work too. Again, nitrite is your problem. get the tank cycled and get rid of the nitrite. in the meantime do large daily water changes (50-75%) to keep the nitrite down.

I have wanted to try the baby brine shrimp but they don't sell them at any of my local pet shops. One store sells the culture for them. I was hesitant to try it out. I haven't done that before. Sounds very beneficial though so I will look into it more. Thanks for your reply!

 

[Byron]

Yes live plants are always beneficial. Yes you can add more sand, it doesn't need to be too deep, 1/4 inch is fine. And yes do daily water changes until nitrite is zero.

 

[coriesinhawaii]

I agree that the nitrite is the main problem. I don’t remember that you gave a value for ammonia but if there is any ammonia present that would be harmful as well. The main way of preventing problems with ammonia and nitrite from harming your fry would be to either raise them in a breeder net inside your main tank or take part of the filter media from your main tank and put it in your fry tank when you start it up.

At this point you could try adding in the beneficial bacteria and doing frequent large water changes but honestly it’s hard enough to raise fry without fighting against an uncycled tank. You would also need to make sure to remove as much uneaten food as possible after feedings to prevent the water quality from getting even more messed up. I usually do this with a turkey baster or gravel vac.

 

[coriesinhawaii]

I have wanted to try the baby brine shrimp but they don't sell them at any of my local pet shops. One store sells the culture for them. I was hesitant to try it out. I haven't done that before. Sounds very beneficial though so I will look into it more. Thanks for your reply!

Did you check if they have frozen baby brine shrimp? That works well too.

 

[Corydoras82]

Did you check if they have frozen baby brine shrimp? That works well too.

I did try frozen baby brine. I still have a lot left in the freezer because when I initially offered it to them, they didn't seem interested and even swam from it like it was scaring them? lol. Now that most are around a month old, I will try offering it again. Is the best way to take some of the fry tank water and soak the frozen brine in that?

 

[Corydoras82]

I agree that the nitrite is the main problem. I don’t remember that you gave a value for ammonia but if there is any ammonia present that would be harmful as well. The main way of preventing problems with ammonia and nitrite from harming your fry would be to either raise them in a breeder net inside your main tank or take part of the filter media from your main tank and put it in your fry tank when you start it up.

At this point you could try adding in the beneficial bacteria and doing frequent large water changes but honestly it’s hard enough to raise fry without fighting against an uncycled tank. You would also need to make sure to remove as much uneaten food as possible after feedings to prevent the water quality from getting even more messed up. I usually do this with a turkey baster or gravel vac.

I tested for amonia and it was in the safe range. Next I used a strip that tests for 9 different things I believe. It was showing nirtite and nitrate and I also had very low alkalinity. The copper was out of range as well. I want to try adding the live bacteria but still a bit hesitant. If I remember right, the shelf life for the live bacteria isn't very long? I think my bottle must be a couple months old at least. I wasn't sure if adding live bacteria could be harmful. If there isn't a high percentage of it back firing, I would love to try adding the live bacteria. I also just added a live plant from the parent tank and they love it. Most of them swarmed right to it and are still hanging around it.

 

[coriesinhawaii]

Yeah I would drop the frozen cube in a cup of tank water and once it’s melted I would suck it up in the turkey baster and shoot it close to where the fry are on the bottom.

The bacteria in a bottle don’t usually have a very good shelf life but I’m not aware of any harmful effect it would have if you follow the dosing directions. Only that it might not work like it’s supposed to if it’s too old or hasn’t been stored properly (including when it was in transit to/from the pet store).

 

[Corydoras82]

Yeah I would drop the frozen cube in a cup of tank water and once it’s melted I would suck it up in the turkey baster and shoot it close to where the fry are on the bottom.

The bacteria in a bottle don’t usually have a very good shelf life but I’m not aware of any harmful effect it would have if you follow the dosing directions. Only that it might not work like it’s supposed to if it’s too old or hasn’t been stored properly.

Thanks for the response. I am going to try that method of feeding the brine shrimp as you suggested. I also feel better now about adding the live bacteria so I will probably give that a shot too. Thanks!