Red Tail Shark Hiding?

Hello all,

I have a 55-gallon tank with 6 angels, 2 dwarf gouramis, 2 Australian rainbow fish, as well as a medium sized red tail shark. I've had the red tail shark for at least 4 months now and since then he's been doing great. About a week ago I used to have 2 red tail sharks, but I returned one as the one that I currently have now (considerably bigger than the one I returned) used to chase around the smaller one. The same day I returned the smaller red tail shark I also changed the scaping of the tank a bit too, I switched out my white gravel for black ones (the rocks are the same size just black instead of white).

On top of that, I introduced 4 angelfish into the tank (previously I had 2, currently have 6). Now, these angelfish are pretty much fully grown, and also came in pairs of 2 males and females. Ever since the day I did all these things (returned the other redtail shark, changed the gravel, and added new angelfish), my red tail shark has been very shy and swims stationary underneath one of the caves in the tank. Prior to this, my red tail shark was always swimming around the tank looking for food.

My initial impression was that maybe the bigger angelfish were showing aggression towards the red tail shark but these angels are very very calm and haven't gone after any of my fish.

Another important thing that I started to notice was that my red tail shark's eyes have become white and puffy. After doing some research I realized the water quality of the tank was most likely the culprit and so I've been doing 20% water changes every day for about a week now. All my other fish don't have the white eyes either it's just the redtail shark.

NOTES:
- I believe the red tail's reason for not being as active is most likely the same reason it has the white eyes
- One thing to note is that the reason I changed my gravel is that the white rocks ended up accumulating some BBA on it, which made the tank look very unattractive
- Another reason I changed the rocks was that there was a bit of algae build up on the decor and especially on the glass and so I cleaned all that up the same day
- I'm also concerned that the red tail shark might not have anything to eat as there's not much algae left and it never really ate pellets or flakes.
- The clarity of the aquarium water is pretty clear, but it's not CRYSTAL clear. I will be buying a new filter cartridge for my HOB filter today.


Can anybody give me some advice on what to do to hopefully make my redtail more active and more importantly get rid of his white eyes?
Thank you in advance!

TANK PARAMETERS:
Ammonia: 0
Nitrite: 0
Nitrate: 5-10ppm
I keep the temperature of the tank around 78-80 degrees Fahrenheit
Using 2 HOB filters with a combination of filter cartridges and filter floss

 

Methylene blue will cure his eyes since the white is cause by fungus growth, but you will need to determine what bacteria or parasite is damaging the eyes in the first place. I would suggest moving him to a Hospital tank or bucket with heater, add Methylene blue and Erythromycin. You will have to do 100% water changes and retreat the tank since MB will kill any beneficial bacteria. You can use MB baths in place of putting it directly in but I find it less effective for treating cloudy eye conditions.

MB is a organic stain and will stain your hands, porceline (sink, toilet), but will come out eventually with water.

If you don't start seeing the eye clear up in 4 days, complete dosage and switch to metronidazole or kanamycin.

 

There are quite a few possible causes of cloudy eyes, fungus being one of them. I would recommend against nuking everything with antibiotics when it’s probably not necessary.

The cause of the behaviour could have just been the drastic change in stock. No other shark to dominate, and replaced by fish it possibly thinks it can’t dominate, and are in its territory. It’s way of life has suddenly been turned upside down and it doesn’t know it’s way forward yet.
The disease was possibly brought on by that stress, and/or your water issue...
It could be bacterial or fungal, so a bactericide or fungicide is the way to go imo. There are other causes that we can presumably rule out... eye flukes (need an intermediate host and wouldn’t be so sudden and isolated to one fish), vitamin deficiency (not sudden), chlorine damage (very temporary, after a waterchange).

What exactly was the water problem?

 

Methylene blue is a fungicide and bactericide (mild) that is very safe for fish. The actual cloudiness in the eye is either a hardening of the cornea (cateracts) over a long slow period, or fungus growing on dead cells within the eye. The infection that killed the cells is either parasitic or bacterial the later of which is most common.

Non-antibiotic bacterialcides are only good for topical infections and not for internal infections like the eye. Most common bacterial infection affecting the eye is streptococcus which is treated with Erythromycin. If it turns out to be parasitic the metrozinadole will treat it but it is less likely than the strept. It is extremely unlikely that it will get better with just water changes

 

...It is extremely unlikely that it will get better with just water changes

I have to disagree.
The most common cause of cloudy eyes is a deterioration in water quality, which allows bacteria to cloud the outer surface of the cornea. It’s often a first sign of the water quality getting bad. If remedied soon enough the improvement in the water quality alone often cures the cloudiness. If not, a bactericide usually will in those cases.

 

I have to disagree.
The most common cause of cloudy eyes is a deterioration in water quality, which allows bacteria to cloud the outer surface of the cornea. It’s often a first sign of the water quality getting bad. If remedied soon enough the improvement in the water quality alone often cures the cloudiness. If not, a bactericide usually will in those cases.

You are and are not disagreeing, with me..
Poor water quality causes bacteria that feeds off the organic material to grow in large numbers and eventually infect the eye. Fungus begins feeding on the dead cells produced by the infection, the fungus is the with substance that gives the eye the cloudy appearance. To point, the fungus is a secondary infection and curing the infection will remove the fungus on its own. Treating the fish to get rid of the fungus allows the fish to see earlier than if you just treat the infection. Even in the case of parasitic infection, the cloudiness is caused by fungus feeding off the damaged eye.
While clean water is the best first level cure, having both eyes clouded up is an indication of the infection having progressed considerable and hoping that the fishes immune system will beat it at this point is a big stretch. Either way, if you don't have clean water the treatment is unlikely going to be able to beat the bacteria's growth rate and many bind to organic chemicals in the tank.