Why are my fish dying ?

[Blahblahblah]

Hello, and thanks in advance for your advice.
I have a 29g tank ( first tank ever. Purchased 12/27/2015. almost 4 months
1 Topfin 30 brand filter with 2 carbon filter cartridges ( 3 months old )
Liquid Prime
Fish in cycled tank
Been doing water changes about every 4-5 days
PH-8.2 ( tap water PH is high)
Amonnia-0.25 ( can't get it lower)
Nitrites-0
Nitrates-10ppm-20ppm ( colors on chart look the same)

4 Black Skirt Tetras
3 Gold Panda Mollies
3 ( 2 Sunburst) (1 Redwag) Platy's
3 Corydora's
2 Male GUppies
1 snail

2 plants so far
API Leaf Zone fertilizer

For some reason my Play's hide in a large rock display. One looks like its been injured. Yesterday I lost a Sunburst Platy. Then this morning I found a dead Corydora. WTH! I did a water change on Wednesday with 6 gallon water jugs with tap water with Prime in each jug before adding to tank. I also added a dose of fertilizer for plants. It had only been about 4 days since I last put it in. Figured since I did the pwc I should put more in. Could that be why they died? Or was it just the fish in cycling that finally did them in ? Should I do another pwc today? I went to Aqadvise and it told me I was at 80% capacity and that I should add another filter system. Do I need too? Should I replace the Platy's ?

 

[mambee]

I would cut back on the fertilizer until things are back to normal. I believe that Prime gives a false positive reading for ammonia, so I wouldn't worry about that.

Try doing a 50% water change. I'm not familiar with your filter, but you can never have too much filtration.

 

[Blahblahblah]

I believe Topfin is a Petsmart branded item. After I do the wc will it be safe to replace the fish ? I bought a fish tank kit so the lid only has a space for the one filter. If I remove the lid ( which as the LED lights in it ) is it OK to not have a lid, but then I would have to buy a light bar ? I would have no idea what kind to get.

 

[ktomminello]

While you're fish in cycling your tank have you gone without doing water changes yet?

 

[mambee]

What do you mean by replacing the fish after the water change?

I don't know the details of your setup, but this is what I recommend:
1. if you have gravel, replace it with pool filter sand. Gravel lets debris and food sink to the bottom and decay.
2. replace your hood with a glass versa-top. This give you versatility in lighting options.
3. go with LED lighting. I recommend Finnex brand.
4. upgrade to a better filter. I use Eheim canisters on almost all of my tanks. I'm not sure if they make one for a 29 gallon tank.

 

[ktomminello]

*I've been using fluval IF40 in my 29g (I have 60 tanks if you count no fish just plants- 45 if you don't) amazon community tank and it works awesome- and you wouldn't have to change your hood.

Remember to use your old filter media in your new filter if you decide to make a filter switch.

I have to disagree with a change in your substrate as this could at this point devastate what good bacteria you have in your tank. Also- as I learned from this site- sand can trap gas bubbles and needs to be poked around.... Though I personally have sand in at least a portion of all of my tanks without proper "motion" the debris stuck in sand has lead to a couple water chemistry issues especially when I first started using it. Gravel was more convenient when I first started as I could jam the gravel vac down into the substrate without worrying. Once I got used to the swirling method sand became a thing of decorative beauty. As long as the gravel is rounded and not jagged your cory should be ok with it. If your gravel is jagged I would suggest adding a thin layer of smooth rounded gravel, not replacing the gravel all together. You could try thoroughly vacuuming your gravel 1/3 of the tank at a time over the course of 3 weeks, monitoring water chemistry in between, but that's only if there is a problem with dissolved organics I believe.

If you have the money obviously the upgrades mentioned would maybe improve your experience, then again it may not. First things first is working with what you have. You're still tentatively cycling you're tank especially if you've been water changing frequently.