Not Sure What's Wrong Or Just Bad Luck

[smurfette]

Firstly, sorry for the long post but I am trying to give as much info as possible.
I have a 30 gallon running now since August
Current inhabitants: 3 zebra danio
3 twin bar gold platties
1 male betta (very mellow)
4 cory (peppered?)
Live plants

Water tests (API master kit)
Amm 0
Nitrite 0
Nitrate 5
PH 7.6
Water temp 77 F

Feeding: mix of flakes, betta pellets, algea wafers, dried tubafax worms (not all the same day), 1 pea day a week, 1 fasting day a week.

Water changes daily preparing with nutrafin aquaplus (ran out) and a new store brand which also removes chlorine, chloramine, and heavy metals.
I change about 1 gallon per day (takes same time as cleaning cat litter box). I also do a light vacuuming of the gravel once a week with a larger water change. So by the end of the week I have changed about 30%. I do have very small maounts of what I think is the brown diatom algae but not on everything.

I have had the platties about 3 weeks and lost 2 about a week ago. They just went realy pale and lost all colour no signs of parsites or injuries. Now one of the females which may be pregnant is staying on the bottom of the tank, hiding and not moving much. Have put her in a breeder net because she is also starting to look pale. Even the other female is hiding alot.

I have an aqueon 30 power filter and reading the posts you say not to change the filter except if it is falling apart and just to rinse in old tank water. does this apply to a power filter as well when it is an all-in-one unit? Not sure but I have now changed the filter 3 times. I seem to lose fish one at a time for no apparent reason.

Any ideas or suggestions? Or am I just unlucky with my stock I am buying (store tanks look good and clean and fish seem active and healthy).

 

[jonnyf84]

Strange one - i hate it when these mysteries hit your tank. Your water condition are perfect, your not overstocked, your filter is a ok unit that has plenty of turnover for your tank.

Always wash any filter media in old water, always. When you say you'v changed the filter 3 times what exactly do you mean? The whole filter or some of the media? What time period did you change these 3 filters or media?
If you have changed the whole filter 3 times then that is very bad news as your tank would go through a whole new cycle each time, however you clearly have liquid test kits so you would have surely realised something was wrong.
Even if you changed your media 3 times or washed it under tap water then your tank would have undergone a mini cycle which would stress out the fish (especially new ones) and therefore would have made them vulnerableto disease, but again you would of noticed changes from your tests.

Are you testing regularly?

None of your other fish are displaying signs of disease? (flashing or flicking, not feeding, hanging at the surface, hiding)

Do the platys have red or inflamed gills?

 

[smurfette]

The Aqueon's filter is like a plastic frame with charcol packed between what looks like white sheet of polyester fiber fill and I replace the whole thing because there is nothing to unpack/remove from it. When I do rinse it is in either old tank water or Brita filter water which states that it does remove chlorine and heavy metals. I had checked with the water company and they never use chloramine.

No other signs from any other fish they are all happy and healthy. The cheeks on this type of platy are bright red and I notice something is wrong when the colour started to fade. From reading other posts I suspect the females were pregnant and possible stressed by the attention from the males.

To be honest I only got the test kit a couple of weeks ago and the readings I gave below were 24 hours after changing the filter. This filter has plastic combs inside which state they hold the bacterial media and these I have never touched.