Major causes of fry loss?

[raymond82]

All my apisto's spawn regularly but I'm a little bit unhappy with the amount of fry that actually makes it to juvenile stage. The latest T. candidi fry hatched, I saw two or three at the entrance of the cave 10 days after I first saw the eggs but the group never became free swimming and at some point the female gave up on them. My gephyra's also spawned many times and I've seen a lot of free swimming fry only a very small amount made it to juveniles.

Now I have two A. eremnopyge nests in two different aquariums and the survival rate differs greatly. Both started out with ~50 fry, one of them still has around that number but the other one only has about 15 left.

I was wondering, what causes the loss of fry after they become free swimming? I can think of a couple of reasons:

- Other fish eat the fry (unlikely since I keep them with Nannostomus spp and the female keeps them away very well)
- Bad water quality (I could only check for nitrite but it was 0)
- Bad parenting/inexperienced mother
- Overfeeding BBS (maybe I feed them a bit too much, could it be that they overeat?)
- Tank too crowded (this is what might have been the cause with the candidi's)
- Hydra (I lost a gephyra and eremnopyge nest recently in tanks with a lot of hydra)

 

[Borelliiguy]

The following may sound harsh but bear with me. Of the causes you listed what stood out like a sore thumb to me was:

- Bad water quality (I could only check for nitrite but it was 0)
- Tank too crowded (this is what might have been the cause with the candidi's)
- Other fish eat the fry (unlikely since I keep them with Nannostomus spp and the female keeps them away very well)

The fact that you list over crowding and other fish eating the fry in most cases would be the causes. It doesn't matter what fish you have or if the mother is super protective. Fish will distract the mother on the right, while another sneaks up from the left. In fact, imo the more aggressive the mother is the easier it is for the fish to be preyed upon because she'll try to injure one fish while the rest feast on her fry.

Secondly it is imperative that you know what your water parameters are. Ammonia, nitrite, and nitrate will kill fry. I aim for 3 zeros and at worst nitrate below 20ppm but that's me.

A trick I've learned over the years is to remove all the fish one week after the pair have spawned. Do it at night, suddenly switch the light on and the fish will be too disorientated to swim away and cause a commotion. Re-home them and give your fry the run of the tank for 7 days. then remove the fry to their own tank and reintroduce the old stock.

 

[Mike Wise]

Since you don't give us enough information on your aquarium, it's hard to say what the problem truly is, but I tend to a agree with Borelliiguy. The primary causes of fry loss are 1: under/overfeeding (under leads to starvation; over leads to 2); 2: water quality (dead fry or food will quickly degrade water quality) and 3: overcrowding, which can cause predation or degraded water quality. More information on your breeding methods might point us in a direction that can help us. Tank size, decor, population, feeding (portions and number of times/day), water value (pH, GH, KH, µS, NH4, NO2, NO3) are useful information.

 

[wethumbs]

In overcrowded tanks, you can remove and hatch the spawn artifically if your goal is to have more fry. Otherwise, keeping just one pair of a trio in a reasonably size tank will solve your issue with fry. Obviously, you still need to keep up the weekly water change.

 

[raymond82]

Thanks for all the input!

I'll explain my situation a bit further, the situation is slightly different in the different tanks and the examples I gave don't apply to all the tanks equally:

With the T. candidi I'm quite sure it's a matter of too many old fry, my guess is that the latest eggs hatched (I saw some swimming) but somehow the female did not take them out swimming. I will remove the older fry (with a bottle, I know how to do it now) to see what happens with the next spawn. In this aquarium all the fry that became free swimming grew up well (two batches).

I have one batch of A. eremnopyge fry (F1, 10 days free swimming) living with the parents and 3 Nannostomus in a 60x30 cm (50 L) tank. They are doing well, I think there are around 50 of them and I don't see many losses. Previously this aquarium had a lot of Hydra and then I saw less fry by the day.

The other batch of eremnopyge fry (F1, 18 days free swimming) is in a tank together with the parents and 5 Nannostomus in a 60x40 (50 L) aquarium. Here I notice that I'm loosing a lot of fry. It's also the first time this female has fry, she's very aggressive and killed another female that was in the tank with them. pH = 7 (that's higher than I expected), 150 µS, KH = 2. The tanks is filtered using air driven filters, one 1L filled with lava rock and a one double sponge filter.

The fourth aquarium is most problematic, I'll devote a new thread to that one cause I see more things there that I don't like.

Here's what applies to all of them equally:
- Weekly 25% water change with peat filtered RO water
- 2x daily BBS feeding (sometimes 1x is substituted by microworms). I find it hard to say how much I feed, but it's quite a cloud.

To cut it short, I think for the T. candidi aquarium the problem is clearly overstocking as suggested above. The second A. eremnopyge aquarium is what puzzles me, since in exactly the same aquarium my A. sp. Vielfleck produced a lot of fry. I doubt the Nannostomus pose too much of a threat, at least they didn't with the A. sp. Vielfleck. That leaves the feeding, I know it's hard to express amounts of BBS, but can you give an indication?

I'll get an ammonia test so I can test that too.

 

[Mike Wise]

Your 2nd A. ermnopyge tank doesn't have optimal water values for some reason, at least for this species. Ideally the pH should be <6.2 and conductivity <100µS/cm. For general health, the values you list will be fine for a clearwater species like A. sp. Xingu (Vielfleck), but not a blackwater species like A. eremnopyge. Blackwater species tend to catch disease more easily in neutral water values. This is probably because, in their natural blackwater environment, there is a lower concentration of bacteria in the water and the fish don't need to have as strong an immune system.

As for feeding, it's like any prepared food. If you see any in the tank after 5 minutes, then you are overfeeding.

 

[raymond82]

I'm slowly lowering the pH and conductivity of the aquarium but I'll speed it up a little bit. I don't think more fry disappeared over the last few days so maybe I'll manage to raise the 15 or so that are left. Otherwise better luck with the next batch of fry!

From now on I'll make sure not to feed too much, keep an extra eye on water values when a lot of fry is present, prevent overcrowding and make sure that the fish are in the proper water.