Schwartz's corys' barbels have worn away and two have died

[bell7797]

Hello, I have a 30 gallon planted aquarium with 4 corys, 6 harlequin rasboras, 2 small zebra loaches, and a bristlenose pleco. It is fully cycled, and the ammonia and nitrite levels are at 0. I also do weekly 1/4 water changes. At the start of the summer I had 6 corys instead of 4. The two that died had virtually no barbels left and then developed a fungus around their mouths. I dosed with pima and melafix and this seemed to keep them from getting worse, but they were not able to recover. I believe that the problem is my substrate (Caribsea Super Naturals Torpedo Beach), but after research it seems like there is no consensus on what substrates work and what ones do not.

I have three questions: Is there anything I can do for the remaining corys so that their barbels will grow back? Are there any other species of corys that are better adapted to a sand substrate? And should I be worried about the loaches as well? The CaribSea website lists the torpedo beach substrate as "soft belly safe" but not "burrower friendly". Any help would be greatly appreciated thank you.

[RickE]

Not familiar with this specific substrate in the UK, but for soft mouthed Corys that like to dig around for food the substrate must be soft/rounded. My guess is that your substrate is a sharp sand which is rubbing away at the Corys mouths as they go about their daily business. You might be able to feel this if you rub some between finger and thumb. I would definitely try a different more rounded substrate.

Although the water parameters you mention are good, you don't mention the pH. I have seen reference to Corys having their barbels 'burnt off' by too low pH although I don't know if it is true.

[Richard B]

After checking the manufacturer website, this substrate looks a little harsh for corys. Pool filter sand, DB aquarium sand (UK only?) are better choices - what you are looking for is something with fine rounded grains. This should not be too deep as it can lead to stagnation problems - this may be a problem as you have a planted tank. What i'd ideally recommend is something along the lines of what apistomaster has, (there are pictues in various threads) which is a terrace effect of a deeper back section where it is planted, topped off with rounded gravel with a front section with a thin layer of fine sand.

[bell7797]

Thank you for the replies. The pH is fairly high here (7.2-7.6). I will definitely start looking for a smoother substrate.

[MatsP]

Thank you for the replies. The pH is fairly high here (7.2-7.6). I will definitely start looking for a smoother substrate.

The pH is indeed above 7, but I wouldn't call 7.2-7.6 excessively high - it's about the same as or lower than what comes out of the tap in most of England, and the tap-water here is fine for most of the common cories (C. schwartzi is certainly not uncommon here at least).

Substrate is highly likely the issue.

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Mats