Patchy disease?

[svan]

* Type of fish that are affected (common name and latin name if possible - common names vary worldwide, latin names don't!): queen loach (botia dario) and also possibly bristlenose pleco (ancistrus sp?)

* How long has the tank been set up for? about 4 years
* Size of tank (dimensions and volume). 20 gallon high / 75 liter; 24"/61c w x 16"/41c h x 12"/30c d
* How is the tank being filtered? Marineland Penguin Bio-wheel 150
* Water temperature. 79F / 26C
* Your current water parameters - ammonia 0ppm, nitrite 0ppm, nitrate 30ppm (this stays pretty constant regardless of where in the water change calendar I am), pH 7.2, kH 5dH.

* Your maintenance regime (e.g. how often water changes are carried out, what percentage of the water is changed each time, how often you clean your filter/s and how do you do this?) 30% water change weekly; clean filter by swishing in removed tank water whenever the water flow becomes restricted so that bio-wheel slows down too much, and change it when that no longer does any good (about every month and half or so)

* Has anything new been added to the tank recently? (fish, plants, live food, decor etc): Over the last couple of months I've had 2 dwarf gouramis and 7 guppies come and go - both gouramis died in quarantine tanks, but all the guppies died in the main tank. Some very well-cleaned shells and small coral pieces have also been introduced, and I changed the substrate (from one type of gravel to another, as can be seen in older and newer pictures of pleco below). Also added anacharis, which had been in the tank previously, and needle leaf ludwigia, which had not. New foods used in this time period include bloodworms and brine shrimp, both freeze dried and both used infrequently and in small amounts (as "treats", basically), and cucumber and kohlrabi slices for the pleco, which she seems to enjoy greatly, although the cucumber did cloud the water a bit.

* What other fish are in the tank? besides the two listed above, just one juvenile guppy

* As detailed a description as possible of the symptoms the fish are exhibiting (remember a photograph can speak a thousand words). The loach has a spot on her head area that kind of looks similar to a stripe in color and even texture, but is new - see photo below. The pleco has basically been changing color - see June vs. August photos below - which I know they can do based on their surroundings, and I did change the gravel color, so maybe this is totally normal, but when I read about patchy disease, I thought that this might possibly be affecting both fish, but I really can't find enough info on it in anything other than hillstream loaches. Neither fish is acting out of the ordinary in any way as far as I can tell, but they're both quite nocturnal so I don't see them do much anyway. The pleco does eat vegetables I put out for her overnight.

* How long ago the affected fish were added to the tank, and how long the fish have been displaying symptoms. The pleco has been in the tank since the very beginning; the loach not quite as long but also for multiple years. The pleco had some amount of patchiness for at least the past several months (perhaps forever, I'm really not sure), as can be seen in the June photos below, but coloring has really changed progressively and fairly dramatically in the last month and a half or so. I first noticed the spot on the loach probably about three or four weeks ago, and I'm not sure if it has gotten larger at all - if so, only a very tiny bit.

So, here is what the pleco looked like in late June (note that I no longer have the blue botia seen in the background of one picture - I got rid of my 2 because they were too big for the tank; also note the old blue/green/white gravel):



And here are the pleco and the loach in the last week or so (note the new brownish gravel):

^This was taken with a flash, so her light colors aren't *quite* as bright/light as they look here.

^Taken without a flash and thus a tad blurry; what looks like white dots near her eyes are just her nostrils.

^Note the spot roughly between the eyes.

[chefkeith]

Sounds like a lot is going on here. The shell and coral should be removed, as they'll leach and alter the water chemistry, especially in such a small tank.
The nitrates should be kept under 20 ppm, so more frequent water changes is needed. Do daily water changes on the smaller side, like 20 - 30%, , until you get the nitrates under control. Once the water parameters are better, the bacterial/fungal infection should start to clear up. It may take a month or so, but you shouldn't need to use any antibiotics to cure them.

Don't add any new fish until this issue goes away. There is also a fish husbandry issue here. The bristlenose pleco should have a partner. The loach should be kept in groups, a small group in this case. With a 20 gallon tank, you will be limited with the number of species kept it in. So a community tank is not ideal here. You'd be best off keeping just one of two species of fish in this tank.

[svan]

The shell and coral are in the tank for precisely the purpose of altering the water chemistry - without them the pH hangs out in an awfully low range.

I would hope it would be obvious not to add any new fish while my current ones are not healthy, but maybe not...

I have never heard that bristlenoses have any trouble being alone. The loach, I know, is not happy alone. Once upon a time there was another one, but it died while the tank was out of my care (my ex had it for a while). I have been planning for some time now to buy 2 more, but the LFS keeps telling me to "check back in a couple weeks" and I wouldn't get the new ones right now even if they were available. Ultimately my plan for this tank is to add 2 more loaches, some more guppies, and then see where things are.

[chefkeith]

Does the water change water match the water parameters of the tank water? When you do water changes, if there is a big difference between the water parameters, you might be stressing the osmolarity system of the fish. With something leaching in the tank, such as coral, the fish will spend most of their energy regulating to the constantly changing water chemistry, thus making them more prone to fungal or bacterial infections. On top of that, a water change may be causing some osmotic shock.

A better method to raise or stabilize the pH is to pre-treat the new water change water. Many fishkeepers do this in a rubbermaid trash barrel when they are aging the water. They'll just soak a sock of crushed coral in the water barrel.