Think My Tank Is Done Cycling, Fish Dying.

[MichaelButera]

This is my first tank, and like many others I had made the mistake of keeping fish in the tank before it was cycled, should have done more reading before jumping in. Anyway:
 
Almost 2 months ago, I bought a 20gal tank. I planted it with three Amazon Swords, and stocked it with 6 Platys and 3 Mollies. Through the course of the cycle I have lost all but two of my female Platys. A couple of the ones that I had lost were after my levels were almost right, definitely a lot better than when I had stuck them in there (

). While the tank was cycling I was doing water changed every 3-4 days, now I change 20% every Sunday.
 
My levels are:
 
Ammonia: 0 ppm
Nitrites: 0 ppm
Nitrates: 20 ppm
Hardness: 75 ppm
Alkalinity: 110 ppm
pH: 7.2-7.8
 
The tank right now: 
 
I've got the two girls in there, one of the plants looks a little weak, another has a completely dead leaf that I will be clipping during today's water change. Every now and then it seems as if one of the fish is going up to the top to breath, but I'm not too sure why. The tank lights are LED and penetrate to the bottom, so I don't think that the plants getting an adequate time to convert CO2 to O2 is the issue. My other thought would have been ammonia poisoning, but my levels have been fine for almost two weeks now. The filter provides quite a bit of aeration on the surface.
 
Please help, I'm confused and want to get this tank to a spot where I can stock it up. Would replanting affect me negatively?
 
 

 

[ShinySideUp]

It does require quite a lot of light to do any good at the bottom of a tank. Just because it looks bright to us does not necessarily mean that the plants are getting enough light. My own tank has 160 watts (T5 lights) total so that there is enough light two feet down.
 
Having said that, be aware that new plants do tend to melt away when new, only to grow back again so long as the crown of the plant (where the leaves grow from) is not buried.
 
You need to confirm your hardness as it is not measured in ppm and your alkalinity, and acidity, is your pH value; at 7.2-7.8 your water is slightly alkaline but nothing to be concerned about.

 

[Byron]

I am assuming you "cycled" with the mentioned fish in the tank.  Mollies are incredibly sensitive to ammonia--all fish are, but mollies even moreso--and while a fish may live through the cycle period, the ammonia and/or nitrite does irreparable damage internally, and such fish always succumb down the road.  At the best, they will have been severely weakened (the immune system) and thus more likely to contract something else that otherwise could be fought off.  I say all this just so you know that the fish deaths are really not surprising under the circumstances.
 
Aside from the nitrogen issues (cycling), the next problem here is the water hardness.  If the GH (general hardness) really is 75 ppm, it is way too soft for livebearers.  Here again mollies are much more highly susceptible but platy won't last long either.  Livebearers require harder water because their physiology needs the calcium and magnesium they assimilate from the water as it enters their bodies.
 
I really am sorry to be the bearer of bad news, but I think you should prepare for the remaining two platies to die.  Even if they are moved to harder water, I doubt they would improve, though of course they might.  Daily water changes of more than half the tank might have helped the fish live through the cycling, but again there would still be internal damage.
 
Turning to the plants, light is the likely issue here.  I have no experience with LED lighting, except one attempt which didn't work and I sold the unit.  But other members with experience with LED may be able to offer advice if you post the light data.  I would hold off on more plants until the light is assessed, and then you will have a better idea of which plants should manage.  Different plant species have sometimes very different requirements when it comes to light; the light intensity drives photosynthesis (which as you may know is how plants grow) and light sufficient for Java Ferns will not be sufficient for most stem plants, for example.
 
The water test numbers, are they from the aquarium via a test kit, or the tap water?  You can confirm the GH, KH and likely pH from the municipal water authority, perhaps on their website.  Now that the tank is cycled, the sort of fish you should consider to restock will be soft water species, which includes most South American, SE Asian species.  Avoid livebearers (assuming the numbers here are basically reliable).
 
Byron.

 

[MichaelButera]

Thanks for the replies.
 

 
 
If the GH (general hardness) really is 75 ppm, it is way too soft for livebearers.

 
I just did the test again, this time on the water coming from the tap too. My lighting must have been poor this morning when I was looking at the strips. The GH is from the tap is between 75 and 150, closer to 75. From the aquarium, it is looking like it is sitting somewhere between the 150 and 300, my guess would be ~200. Not sure why there is such a discrepancy. All of my other numbers are accurate though.
 

 
 
I am assuming you "cycled" with the mentioned fish in the tank.

 
Yeah, like I said, I unfortunately made that mistake. If I can't keep live bearers, would some cichlids do well in a 20gal tank?

 

[Byron]

Depends upon the cichlids.  While a 20g would suit a small group of the "shell dweller" rift lake cichlids, these are much harder water fish.  The rift lakes are about as hard as freshwater gets for fish.  The smaller cichlids from South America are obviously soft water, so that may be an option.  The Central American cichlids are all larger tank species, and obviously moderately hard water (the livebearers come from this part of the neotropics too).  But the hardness of the water needs some investigating to pin it down.
 
To the GH numbers.  Track down your municipality online and you may find the water data to confirm your numbers.  Test strips are known to be difficult to read, and some are not always that accurate.  Generally, the GH will remain much the same in an aquarium, unless it is specifically targeted.  By this I mean that the aquarist is doing something that increases (or decreases) the hardness.  The latter (decreasing) is much more difficult but the former is much easier.  Rocks, gravel and sand that are composed of calcareous mineral (calcium primarily, but also magnesium and sometimes a few others) will slowly dissolve, increasing the GH, and simultaneously the pH.  So, if in the end you find that the aquarium really is as much of a difference as 75 to 200 ppm, it is almost certainly going to be the substrate or rock if any, or both depending.
 
I would not recommend acquiring any fish until the GH is pinned down.  GH does impact fish, all fish, one way or the other.  Deciding on fish that will suit your source water is much easier and safer, though if you have a calcareous substrate and you can confirm the numbers, that will work too.
 
Byron.

 

[Munroco]

"some cichlids"!!!!.... there are thousands of species of cichlids. These are living creatures so please do them the courtesy of at least researching some of the species you wish to keep.

 

[MichaelButera]

 
 
"some cichlids"!!!!.... there are thousands of species of cichlids. These are living creatures so please do them the courtesy of at least researching some of the species you wish to keep.

 
That's what I am doing. I am consulting people that are a lot more knowledgeable than me so I can get a push in the right direction, so I can do my research on a group of species, not learn all of them.
 
Thanks for the input Byron, I appreciate it. I'm looking into the water data.

 

[StevenF]

I just did the test again, this time on the water coming from the tap too. My lighting must have been poor this morning when I was looking at the strips. The GH is from the tap is between 75 and 150, closer to 75. From the aquarium, it is looking like it is sitting somewhere between the 150 and 300, my guess would be ~200. Not sure why there is such a discrepancy. All of my other numbers are accurate though
 

.Every time you feed the fish you add minerals to the water.  Whenever your water evaporates it leaves minerals behine.  That is why we cycle water on a regular basis (once a week).  If you are replacing enough water every week your water harness should be the same as your tap water.  If it is 200ppm then you are not cycling enough water out of the aquarium every week.  If you don't cycle enough water Phosphat levels will climb and that often leads to Algae problems.