Missing Scales - Goldfish Help

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Aquarium Advice Newbie
Jun 22, 2023
My partner has had a goldfish (Black boar?) since she was a teenager, he must be 14 or 15 years old now.
When we moved in we transferred him over to a 400L tank so he has loads of space. I give him a partial water change once a week. He's been in this tank for 4 years now.

He's got lots of live plants but they do tend to die after a few months (Not sure if i'm doing something wrong there, I do use a plant feed)

My main problem is that he's recently lost some scales (See picture)
From water tests it seems that ammonia levels are fine, which is what google pointed me to. The other conerns are hardness (A bit too hard) and high Nitrate levels. I've added more plants and completed a couple of larger water changes (with rain water) to try and bring down the nitrate but to no success.

Could the nitrate be causing the scale loss?

Thanks in advance for any help!



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Hi Ben and welcome to the forum :)

Nitrates don't cause scales to fall out but do cause health issues that can shorten a fish's life. The easiest way to reduce nitrates is with a 75% water change and gravel cleaning the substrate every day until the level is down to 0ppm. Then do a 75% water change and gravel clean once a week after that.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

Check your tap water for nitrates. If you have nitrates in the water supply, you will only be able to drop the nitrate in the tank to the same level as the water supply.


Hard water is not a problem for goldfish and they do best in water with a GH (general hardness) of around 200ppm. You can contact your water supply company by phone or website to find out what the GH is.


Can you post another picture of the fish showing it from the side?
Check it on your computer to make sure it's in focus and clearly shows the missing scales.

The fish isn't a black moor. They have big bulging eyes and 2 tails (fantail).
The fish in the picture appears to be a bronze or black common goldfish. These usually have fewer health issues than fantail (double tail) goldfish.

The fish appears to be very skinny. What are you feeding it and how often do you feed it?
What does the fish's poop look like?


Goldfish naturally eat a lot of plant matter and at least half of their diet should be plant based.

If the plants are dying it could be caused by lack of light, terrestrial plants sold as aquarium plants (these drown underwater), or the goldfish is eating them. If you can tell us the names of the plants or post pictures of them, we will have more idea what is going on with them. Also tell us what type of light is above the aquarium and how long it's on for, and what type of plant fertiliser you use.
Thanks for the detailed reply and apologies for my lack of knowlege!

I don't think the water supply is an issue - we use a rain butt to refil as our tap water wasn't good quality. That being said I will test the water butt just in case.

He has missing scales on both sides though the side I previously uploaded is newer and larger. The ones on the other side are older and have now dulled (i'm assuming where the scales are growing back) I wasn't really concerned to start with but it's just as it's now on the opposite side ( a couple of weeks later)

You are right on the species, I think he could also be a black comet though i'm not sure.

I feed him tetra granules twice a day but there are also plenty of live plants - some of whch he actively eats, and I have to regularly clean out floating leaves with bite marks. He is quite large so not sure if the previous picture makes him skinnier than he is, maybe the new photos will help

In regards to lighting, his location gets an hour ish of direct light in the mornings but we also have a large aquarium light above him. I've generally been leaving it on for 7 hours a day but I did read something about using it less as too much light can also be harmful for the plants

There is a mix of plants, some planted into substrate and some in containers. We definitely have Amazon Sword, Anubias, ammania, and Alternanthera (He eats this the most)

Ther fertiliser I've been using is TNC Lite without Nitrate and Phosphate.

Thanks again!


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Comet goldfish have a longer tail than common goldfish. Your fish is a common goldfish.

Plants can have up to 16 hours of light per day but must get at least 8 hours of darkness to rest. Most people have aquarium lights on for 10-12 hours per day. Lack of light (not enough hours per day or not enough intensity/ brightness) can harm plants. The easiest way to judge the amount of light you need is to monitor the algae and some plants.

If you get lots of green algae then reduce the light by an hour a day and monitor the algae over the next 2 weeks.
If you don't get any green algae on the glass then increase the lighting period by an hour and monitor it for a couple of weeks.
If you get a small amount of algae then the lighting time is about right.

Some plants will close their leaves up when they have had sufficient light. Ambulia, Hygrophilas and a few others close their top set of leaves first, then the next set and so on down the stem. When you see this happening, wait an hour after the leaves have closed up against the stem and then turn lights off.


I can't tell much from the pictures (digital cameras hate black, white or yellow objects). The scales might be getting ripped out if the fish gets caught on something like the filter. As long as the area doesn't become white and fluffy (look like white hairs sticking up), or develop a red sore, it should be fine. If it does go white and fluffy it is Saprolegnia fungus and salt can treat it. If it turns into a red ulcer/ sore, then salt or a medicated fish food that treats goldfish ulcer disease. But right now it looks more like a few missing scales that should heal without any issues.


You can add things to the diet. I used to offer my fish marine mix, which is a frozen fish food made up of prawn, fish & squid. You can also buy marine green, which has the same but also has algae or spinach in it. I prefer the standard marine mix.

If you have raw/ cooked prawn/ shrimp in the freezer, you can defrost one, remove the head, shell and gut (thin black tube in body) and throw these bits in the bin. Then use a pair of scissors to cut the remaining prawn tail into small pieces and offer the fish a few bits at a time. Feed until the fish is full. Do this a couple of times a week and the fish will love it.

You can also offer them aphids from the garden, small flies and mosquitos that have been caught without chemicals. Some fish will eat ants and ant eggs but you have to see whether your fish does. Generally most small non-toxic insects can be fed to fish as long as they are free of chemicals. You use these foods in addition to the dry food. So you feed dry food first and then offer some live or frozen foods.
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