What does "food safe" mean:rolleye1:? You seem to be hung up on a catch phrase that has little bearing with regard to materials within a reef tank. Our tanks have nothing to do with "food" and everything to do with complex biological systems with relatively delicate organisms housed in a closed environment. The FDA has nothing to do with our hobby and their "seal of approval" really doesn't mean much beyond human consumption. Lets look at a prime example: cyanoacrylate aka super glue. Yup, the glue used to attach corals to rock is considered to have a "mild toxicity" because the fumes can react with moisture when inhaled :lolspin:. Yet this same substance has been in use for decades, with great success actually. On the other side of the coin, copper is highly toxic to the organisms we are trying to maintain in our systems yet has been used in cooking pots and water pipes for centuries. What applies to humans does not directly transfer to reefs.
When it comes to tank crashes, you need to dig deeper:fish1:. I've yet to find one that had a root case in some infinitesimally low chemical concentration. It was either equipment failure (an exploded heater, a seized pump :mad2
, outside factors (power failure:rolleye1
, or most commonly it was gradual decline due to a lack of upkeep :uzi:. Folks get complacent and allow detritus to collect over time. Filter socks don't get changed as often, skimmers don't get maintained, pumps are fouled with algae, no water changes. All of these things can stress the balances in a tank until some "plague" takes over and then things snowball. Algae starts taking over, which kills the corals, which fuel the algae growth further. The clean up crew isn't replenished so there aren't as many algae consumers anymore. Eventually it all goes bad and the owner gives up the ghost on the whole thing. But the first action that caused it all? The human not doing the routine jobs. The materials in the tank had nothing to do with it :hammer:.
You say the use of egg crate hasn't been studied. I would disagree. Hundreds of reef systems over the last 20-30 years can't lie. The place I purchase my corals from is an aquaculture facility that's been running for the last decade. They literally GROW corals in tanks that have the entire bottom lined in egg crate. If there was something toxic coming off that plastic, I would think they would have seen problems by now. They are the only licences aquaculture facility in Maryland for corals and do research for pharmaceutical companies and government agencies. I'm pretty sure that what they consider safe to use in their setups is safe to use in ours. Just my opinion.
Turning the substrate is for FW, not SW, at least not manually. The critters in the sand do the work and they have no problems with a little obstruction in the lower reaches of the sand bed. It's no different from them hitting a buried rock, they just work around it. Bristle worms have a bad reputation considering how useful they are at removing detritus from a setup. You would do well to have a few in your tank. Having them take over means you have something else wrong and they are the symptom of the problem, not the cause.
One way to ensure the substrate is suitable is to get the proper size and have enough of it that the critters working the surface never see the egg crate. While I put down the grid and then the rocks, I have a 2"-6" sandbed across my entire tank. Even where the flow has carved out low spots, there is still a good covering of sand over the plastic. My snails and hermits never see what's at the very bottom of the tank. With a couple inches of sand, the bottom 1/4" doesn't do much.
Please try to realize that there are no absolutes in this hobby. There are things folks know will harm your system (copper being the big one) but there is a lot about the systems we keep that is hidden from us. Anecdotal evidence may not have much bearing in the science community but sometimes anecdotes have a basis in truth. On more than one occasion the reef community has shown the science community what works and what doesn't simple because we are willing to do some trial and error. The point is to figure out where the errors are, avoid them, and keep moving forward. There is no one right answer, only things that work for some folks more than others.
Good luck,
.
