High nitrates

Swartz44

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I have a 20 gallon freshwater aquarium since september of '20. I have 2 angel fish, 1 red tailed black shark, 2 guppies & 1 algae eater. I also have 3 live plants & assorted artificial plants. Anyway my ph sits around 6.6, ammonia & nitrite are 0ppm but nitrates are 80 ppm or slightly higher. I do 25% water changes and siphon the gravel once per week my temperature is 77 f and I use Kent marine pro plant 3x's per week with my live plants.

Anyway I had 2 gold dust mollies & 2 black mollies that were healthy for a couple months & then , one by one, all got this "sunken in stomach look" and died. The other fish look great & eat well. Any suggestions for my situation? Am I doing anything wrong possibly?
 

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Essjay

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That's an awful lot of fish for 20 gallons! And fish that need bigger tanks.

The pH at 6.2 suggests that you have soft water. Can you look on your water provider's website please to see if they give your hardness - you need a number and the unit of measurement.
Mollies are hard water fish and will become sick very easily if kept in soft water. This could be what you are seeing.
Did the mollies do normal poop or did they do white stringy poop?
 
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Swartz44

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That's an awful lot of fish for 20 gallons! And fish that need bigger tanks.

The pH at 6.2 suggests that you have soft water. Can you look on your water provider's website please to see if they give your hardness - you need a number and the unit of measurement.
Mollies are hard water fish and will become sick very easily if kept in soft water. This could be what you are seeing.
Did the mollies do normal poop or did they do white stringy poop?
White stringy
 

Essjay

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That sounds as though they also had an intestinal infection which could be worms or a protozoan infection. If it's worms, the other fish in the tank will also be infected.

 

Mick85

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I'd take some of the fake plants out and replace them with live plants. Live plants absorb the nitrates, plus your fish will enjoy them a lot more and just helps balance the tank out.
 

Essjay

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I missed the nitrate level!

We should aim to keep nitrate below 20 ppm. There are several reasons it could be this high:
High in tap water - though it should not be more than 50 ppm at the most
Overstocked tank - this is applicable here - the more fish there are, the more ammonia they make which is turned into a lot of nitrate.
Over feeding the fish - uneaten food decomposes to ammonia which is turned into nitrate
Water changes not often enough or big enough. Water changes remove the nitrate made by the nitrogen cycle.
In sufficient cleaning of the filter - all the fish poop and uneaten food collecting in the filter decomposes to ammonia which is turned into nitrate.




On a different note, the green and white stripey plant to the left of the skull looks like a dracena which is a houseplant not an aquatic plant - though many fish stores do sell them as aquatic plants.
 

Colin_T

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Check the tap water for nitrates. If the tap water has low or no nitrate, then do a 75% water change and gravel clean the substrate every day for a week. Then do a 75% water change and gravel clean the substrate once a week from then on.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

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Livebearers like mollies, guppies, platies and swordtails are regularly infested with intestinal worms, and this can cause stringy white poop. Deworm the fish and they should be fine.
 
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