Random fish deaths

Question
Well, I actually found the missing zebra danio.  She was still alive but stuck in the base of the same plant that the balloon was found in.  Since she had been in there for days she was deformed/injured and I put her down, poor thing.  I don't know how she got stuck but I think she might have been trying to spawn since she was the biggest of the females.

I do tend to overfeed a little, hence the shrimp.  I've been giving them some extra food and I've found they really like the earthworm flakes when they sink to the bottom.  Plus I think they have been eating some of the fry, yum yum!  My nitrates aren't quite 20ppm, but inbetween 0 & 20 according to the tests.

For the livebearers I got only females as I don't want to be over run with fry and I didn't want to throw too many in at once.  I was planning on adding a few more platies/swordtails, but I was SO happy with my balloons.  I had one for over a year and he died a few weeks ago which just broke my heart (dropsy).

How many zebras do you think I should have?  3 of them are the glofish zebras (which I know many don't like, but they were stuffed in a tank at the fish store and I was looking for zebras...) and 2 are normal.  They all seem to chase and play a lot, I think a lot of it is mating behavior.

The tank is 25 gallons, like a 20 gallon only taller, which as I understand means I can only have as many fish as are in a 20 gallon since the water surface area is the determining factor.  How many of the zebras, platies, swordtails do you think I can fit in there?  The only other fish I was going to add (other than more of the same) is a rubbernose pleco (been wanting one for some time just no where to add one).  

Thank you so much for your help!
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-----Question-----
I don't understand what is going on! I've had fish in my tank for over a week and it is totally cycled thanks to gravel and ornaments from a healthy, established tank and bio-spira.  The tank has 5 zebra's, 4 white clouds, 1 balloon molly, 1 platy, 1 swordtail and 3 amano shrimp.  The stats are: Ph-7, Ammonia-0, Nitrite-0, and Nitrate-20ppm.  Two nights ago my healthiest zebra disappeared without a trace (I looked EVERYWHERE inside and outside the tank) and then last night one balloon molly died.  She was found in a plant this morning.  Both were happy, healthy and eating before I turned off the lights and then were gone!  Any thoughts on what could be going on?
-----Answer-----
Good morning, Martha, thank you for your question.

Your nitrates are a bit high for such a new tank. I don't suspect this is the problem, but you should determine why your nitrates are already at 20 ppm as this is the maximum amount that is considered acceptable. Do you have an undergravel filter? Are you perhaps overfeeding? A small pinch of flakes twice a day should be sufficient, although you will want to supplement this with frozen foods and vegetable matter such as peas, lettuce, zukes and cukes.

I have never used BioSpira, but have heard glowing reports from the majority of users. While I am a little "old fashioned" and would never buy such a product unless I had an emergency - I don't mind the wait, since I usually redo the decor 7 or 8 times anyhow! - I do believe it works. You do have to follow the instructions *exactly* and it needs to be kept refrigerated, even though Marineland makes the claim that it can be kept at room temperature for up to 6 months. Marineland's website is unresponsive, or I could probably give you more information straight from the horse's mouth...

You do mean zebra danios, right? Your community sounds fine, except that all the livebearers would probably appreciate having more of their kind. Platies and swordtails can interbreed, but seem to each prefer having another of their kind to interact with as they will not generally socialize except to fulfill the breeding need. I have twice kept single swordtails and they have never lasted over a year.  

Zebra danios (as well as most of the danio family) are actually a bit aggressive. They are easily startled and can be nippy - both of these traits minimized by shoaling. I would not completely rule out the possibility that your danio jumped out. This happened to one of my danios after I had been using a shoal as dither fish and I found the teeny dried up carcass months later, far from the tank. I have no idea how, but I suspect there was feline intervention!

You should also vacuum your gravel and see if the zebra danio body is not the reason for the nitrate level being a little high, while still acceptable. As for your balloon molly, while I am not a fan of these mollies (they seem to have trouble swimming, their distincitive shape is actually selective breeding of a deformity, in the same vein of bubble-eyed goldfish - beauty is in the eye of the beholder!) they do seem like they need some salt to thrive.

I cannot say why the death was so sudden - she may have been pregnant, adding to the acclimation stress. It's awfully hard to tell with these kinds of mollies. However, since your Amano shrimp can tolerate some salinity and no one else will mind, I would add 1 tablespoon of aquarium salt per 10 gallons of water for the benefit of the remaining livebearers. What size is your tank, by the way?

Do make sure that your Amano shrimp are getting enough to eat, since your new tank will not have much algae present. Even when algae forms, they will still benefit from foods such as spirulina, kelp, and plankton. The latter are used as breeding conditioners but seem to also help with molting and general well-being. Flakes and brine shrimp will be consumed by your Amano shrimp as well as your fishes.

Good luck, Martha! Sorry I could not help you more specifically, but I would keep an eye on those nitrates. While the level it is presently at is not a concern, what is driving them up might be - in the future.

Happy new year,
Nicole


Answer
Hi again, Martha!

I happen to be online but am just leaving, however I can quickly and easily answer your question.

If you are not planning on having any more balloon mollies and want only to have zebra danios, platies and swordtails, I believe that six zebra danios, three platies and three swordtails would be just fine. If you are planning on having all females, fry should not be a problem, except that they are able to store male's sperm for six months or so. If you are planning on having a male in the trio, I would consider acquiring some tetras or really any other fish you may like, that will help with the population control. You seem to be of my way of thinking that, it isn't murder, it's nature! Fry do make among the yummiest and healthiest of snacks...

The rosy barbs in my community tank of '02 kept the platy population in check. They would also light up a coppery red that was almost like they had swallowed little LED lights!

I have never had a rubbernose pleco but have had success with my bristlenose plecos. The dwarf plecos make me wonder why anyone still sells a common plecostomus! Much more bang for your buck. The true rubbernose is only 5" so do be sure you aren't sold another L variety as they are commonly mislabeled. We have a number of shoddy LFS(s) here in Central Florida and I have learned that independent research is your only friend, more often than not. Check out wwww.plecofanatics.com for some pictures!

Take care Martha, and feel free to write back except I may not be able to get back to you until tomorrow.

Cheers,
Nicole