1. How big is your tank:  Gal / litres  -20 gal

2. For how long has the tank been set up:- 1 month

3. How many fish: 4

4. What kinf of fish: 1 orange oranda 1 calico 1 pitbull Plecostomus 1leopard? Plecostomus

5. What are the water parameters:    Ammonia.........ppm  I do not know this
                                                            Nitrite..............ppm
                                                            Nitrate.............ppm
                                                            pH.......................... 6.8-7.0
                                                            Temp...............degrees Celsius / Fahrenheit 72

6. How often do you perform water changes: I have changed the water 2x since I set up the tank

7. How big are your waterchanges:      ......50- 60%...............%

8. What kind of waterconditioner are you using: Seachem neutral regulator adjusts high or low ph removes chlorine, chloramine & ammonia

9. Do you add beneficial bacteria: I added stability 1 capful per 10 gal when set up the tank and another capful at last water change which was a week ago

10. Symptoms your fish is showing: orange oranda has black edging to back fins... this just came up

11. Since when does your fish show these symptoms:    i just noticed today actually about an hour ago

12. How is the normal behaviour of your fish: both goldfish are active, friendly, curious,

13. How do the other fish behave: the plecos are solitary and active. I feed them algae thins by top fin which the goldfish love and will steal from plecos and each other

14. Post pics of the sick fish:

15. Do you have a filter on your tank, what kind, how big (gallons per hour) yes... came with start up set...a top fin for a 20 gallon tank. unsure how many gallons per hour. hangs over the back

16. Do you provide extra aeration with an air pump and air stone/diffuser of some kind. yes


The oranda also was trying to get to an algae pellet between some rocks several days ago and got wedged in between, i got her out (Lucy is her name) and so she has a couple white patches where she scraped her scales and she had also scraped her tail fin that is now edged in black. I have since rearranged the rocks to avoid that happening again. I think she has some sort of infection from that ... but not sure. If anyone can help me out I would deeply appreciate it.

I would do a big water change because the black is amnoia burn from bad water quality.

I would also get some goldfish salt and add according to the container to heal the scales.

If you can, I think a water test kit, that can test not just for ammonia, but nitrite, nitrates and ph would be helpful too

Black could mean an ammonia burn, but black can also be a sign of healing (possibly linked to the fish getting caught in the rocks as you previously mentioned) so testing the water will help us know which one.
Did you cycle the tank before adding the fish?
I would also increase the amount of water changes, with goldfish being very messy fish, you will want to ideally be doing 50% water changes, weekly.

May I also ask why you have a leopard pleco in the 20 gallon with the goldfish? From a quick bit of investigating the leopard pleco I believe can reach up to 20 inches, you will need to upgrade your tank, if you wish to keep it.

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"The Leopard sailfin pleco can be kept in a 90 cm (36 inches) aquarium until it is about 12 cm (5 inches) long. As it grows bigger you will need to move it to a 300 litre (80 gallons) aquarium that measures at least 120 cm (48 inches)."

plecos will eat the slime-coat of the goldfish...this can lead to fatal illnesses

You did the right thing by returning the plecos. The leopard pleco would eventually grow too big and overwhelm your 20 gal tank.  If you're going to buy a test kit, get the API liquid master test kit.  Having a water test kit is not really optional if you intend to keep fish.

I haven't read through the comments, just your post but I think what your fish is got is a fish disease called Ulcers! I read online today, and it is caused by a wound your fish got from gravel or rocks (like you said) that has got infected. The most likely cause for this is very poor quality of water, or very high pH level. Test the water for signs of ammonia and nitrite. Conduct a large water change to reduce pollution levels. Fish lose salts quickly through open wounds, so add aquarium salt at a dose of 1-3g/litre. Use an anti-ulcer treatment. If treatment fails, a vet can prescribe stronger antibiotics.

Hope it helped!

Cal I'm a little confused how you've jumped to ulcers and open wounds?

Kendra do let us know how the fish is doing, has the black faded at all?