Can coralline etch glass? Roughness after srcraping

[Hal]

I just finished scraping all the old coralline off the glass of my empty tank. I used a credit card and a spray bottle of vinegar. After finishing there appears to be a cloudiness in the areas where the coralline was. It feels slightly rough to the touch as I slide my fingers across it. Is it possible for coralline to etch glass or do I just need to scrub more? Have you ever seen this?

[IdahoCindy]

Coralline definitely etches glass permanently.

[Hal]

My research is mixed. Some people say it cannot. Others say yes,and have tried muriatic acid without success, which is what led them to think its etched.

Looks like I'll try muriatic acid diluted 100:1.

If that fails, then a slurry of cerium oxide and a microfiber cloth to try to polish it out.

I will never let coralline get a toe hold on my glass again.

[norfolkgarden]

Haven't seen the tank dry in five years except for the one day we get a massive clean out after the tank crash.
I scrape coralline off the front glass every other week but at least with the water in the tank I haven't noticed any etching.

The glass is plain old old school float glass.

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[MarkW64]

Yes, coralline can definitely etch glass. I have a highly etched 180 in my basement to prove it. I let coralline stay on the back glass (actually it was a peninsula so the "back" was also supposed to be a viewing side) for an extended period. When I finally scrapped it, cloudy patches were left behind in the pattern of the coralline. Vinegar made no difference. Even a good soak and scrub with fairly strong muriatic acid made zero difference. I had never heard of, or been warned about this possibility. I even asked several of the "big names" at MACNA 2012 (Sprung, Yaiullo) who said they'd never heard of it.

No time to write more tonight, but if anyone cares to hear it I can explain further how I eventually received a likely explanation as to what had happened to my glass and why, and how it strongly influenced my decision about which custom tank builder to have make my replacement tank.

[jda]

Mine always come sparkling with Muratic and some minor elbow grease - I never had the softer low-lead glass, though, so this could be different. Vinegar is like throwing a baseball at a freight train next to Muratic acid. I would use it more concentrated than 100:1 - I have used it straight in a dry tank with a plastic scrubber on a stick.

I would really like to know if this is a "normal" glass or starfire thing? I just have normal Oceanic tanks from the 1990s and 2000s.

[MarkW64]

I would really like to know if this is a "normal" glass or starfire thing? I just have normal Oceanic tanks from the 1990s and 2000s.

My etched tank was a "normal" Oceanic from 2004. About twenty months ago I got in contact with Dan Engmark. He had been with Oceanic at the time my tank was built. He was now the CEO of DeepSeaAquatics (DSA, which has since gone out of business). He told me that at DSA they were sometimes getting complaints that glass was getting cloudy. Eventually they even had some of the cloudy glass analyzed in a lab. Here is what he told me they found:

"Float" glass, which is what aquariums are made from has a "tin side" and an air side. If a tank was built with the tin side in contact with the water, sometimes it became etched. This seemed to occur in tanks that had high/fluctuating alkalinity. It also tended to be larger aquariums with thicker glass. After seeing pictures of my damaged glass, and learning that I left the coralline on for an long time, (as well as using Reef Crystals for infrequent water changes without ever testing my alkalinity) he was certain that my glass was etched in the same way.

Dan told me that several years earlier, after discovering this, DSA began making sure all tanks were built "tin side out". I began the process of having DSA build a replacement tank for me. Unfortunately it was only a few weeks later that they went out of business. As I considered my custom builder options I asked them all about their build practices -- my wife wasn't going to agree with the huge expense of a new custom without assurance the same thing couldn't happen over again! The responses were all over the place ranging from "I don't know what you are talking about" to "Of course we build tin side out.