Hi there Bob,
I have a 60 litre moontank and have had it only a week. In the bottom we have shell grit (small pieces of shells), and a fake anemone ornament, filter, heater, and two clownfish in the tank. I noticed after we had the tank running for 4 days that there is a build up of what I'm guessing to be calcium on the glass from the shell grit. I did wash the shell grit before I put it in there, but obviously not enough. I took a water sample into our local pet shop for testing and they said that everything is where it should be for a new aquarium, but the hardness was off the scale, and the only thing they could come up with was that the calcium powder from the grit could have sent it up. We also have what looks like cobwebs growing on the anemone ornament. The pet shop said that they have never heard of anything like that before. I tried to net some out, but it just came back again, and then when I did a half water change I took the ornament out and cleaned it completely, and the next morning it has grown back again. Do you have any idea what this could be??
Hope you can help.
Thanks for your letter and welcome to the hobby, however, your letter alarms me! Let me begin by saying the practice of putting fishes in a 12-gallon tank that has not yet cycled is quite dangerous to their health! Its something I don't recommend nor should a 'good' aquarium shop. Since you're apparently using dead sand/substrate and make no mention of live rock, I see a system where fish waste and their food will create a buildup of ammonia that can be fatal to its two fish, as clowns are not considered to be as sturdy as some other damselfish for starting a new system.
Keep in mind the 'nitrification' cycle, consisting of various bacterium, must be established and properly working to reduce toxic chemicals (ammonia) introduced from fish waste and uneaten foods to far less dangerous chemicals (nitrite/nitrate). This cycle of reduction is commonly called the 'Nitrification Cycle.' And in such an initial sterile environment such as yours, it may take up to two months to properly establish the cycle. I highly recommend introducing some live rock to hasten the cycle, and keep a close look at the water's ammonia level. Again, if not sure about these aspects, check with your local shop. If you see your fish breathing quite fast/hanging near the surface, remove them and bring them back to the shop along with a water sample for them to check. Then ask them how to proceed from there, or come back to me for further help.
And yes, this shell grit can create a high hardness content if not washed thoroughly. And hardness is a somewhat incorrect term in the marine hobby - its properly termed 'alkalinity.' The coating on the panels is no doubt a calcium carbonate dusting, and can be wiped off without harming anything. It will dissipate in time.
As for the cobwebs, have seen these bacteria growths from uneaten food, especially in un-cycled tanks. I've also seen something similar on unwashed rubberized ornaments, as they are usually coated with a silicon-based grease to make them easy to get out of their injection molds (this grease will also neutralize the skimmer process). Therefore, recommend monitoring the amount fed, and also removing the fake anemone 'again, and thoroughly scrubbing it in hot water with a sturdy brush.
Hope this helps,