I have bad luck with Coris...

Naughts said:

Orange pectoral fins is natural colouration for sterbai.

What type of sand do you have? It looks ok but the cory's barbels look short and sharp sand can damage the barbels.

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AdoraBelle Dearheart said:

I also see a seashell in the pic. Those leech calcium into the water and affect your water hardness and pH, not a good idea in a tropical tank. While your hardness is okay for your stock right now, with things like seashells in the tank changing the hardness, each water change is going to cause a slight fluctation, and we don't want fluctuations, stable is always better.

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Hokieokieamy said:

Thank you! Does this still pertain to my seashell if they were store bought and boiled in water before adding to tank?

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10 Things You Shouldn’t Put In Your Fish Tank

If you’re at the stage where you’re ready to set up your fish tank, you’ve probably done a lot of research. You most likely know what size tank you’ll need, how to set it up,

www.fishkeepingworld.com

NCaquatics said:

Itll bring down the nitrates unless you have nitrates in your tap water already.

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AdoraBelle Dearheart said:

Yes, it still applies, because it's what sea shells are made out of that affects your water parameters.

10 Things You Shouldn’t Put In Your Fish Tank

If you’re at the stage where you’re ready to set up your fish tank, you’ve probably done a lot of research. You most likely know what size tank you’ll need, how to set it up,

www.fishkeepingworld.com

.

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NCaquatics said:

Itll bring down the nitrates unless you have nitrates in your tap water already.

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essjay said:

What is the nitrate level in your tap water and how high does it get in the tank just before a water change?

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essjay said:

If tap water has zero nitrate but it gets high in the tank, you need to look at why.

Just how high does it get in the tank?

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essjay said:

Does the fertiliser contain nitrate? It could be listed in the ingredients as either nitrate or nitrogen.

Going up from zero in tap water to 40 ppm in the tank is not good. If the fertiliser does not contain it, we need to find out why it gets so high.

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essjay said:

The first ingredient is nitrogen, but I can't see how much as the % disappears round the edge of the bottle.

My plants are mainly slow growers and floating plants. They get enough nitrogen in the form of ammonia made by the fish so I don't add any extra.
Could you tell us what plants you have in your tank, and what fish (with numbers) so that members who know more about plants than me can take a look. It is possible you don't need to use a fertiliser which contains nitrogen - that is the implication from the nitrate level in your tank. If it is 40 ppm from a tap level of zero, the plants are not using it all.

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