"Just add water" reef...is it possible?

[chrisnif]

I'll explain. My LFS has a big tank, not sure of the gallonage but its 8 feet x 2 feet and at least 2 feet tall. This is their "nothing in here is for sale" reef. I was discussing with the "fish guy" about fragging me some pieces of coral they have in it and he's willing (awesome and dirt cheap because they're all YEARS old). We were discussing the upkeep of said large tank when he showed me something, the sump has a 3-4 in deep bed of crush coral, no pads no nothing, the CPR on the back, yeah it hasnt worked in "years" he said, and water, HA, tap in, never does water changes. Thing tests out on spec in every category i can imagine to worry about in a reef (pH 8.3, A0 Nitrite 0, nitrate 2-3, and calcium is 550ish). What gives?
Now I'll say, this is near fishless reef as the giant hairy mushrooms have eaten the school of chromis down to 2. But he has at least 20 frogspawn that would sell for 30 bux, spiny oysters, montipora, acropora, lots of palys/zoos, mushrooms as above.
I would never go this far, but maybe has this tank just "balanced itself" ? The montipora is growing well that's what im getting a frag of, and i think that might be at least a bit sensitive?

I do all this work and he has a "just add water"

 

[socalnano24]

Its my understanding that a large enough bed of crushed coral can buffer alkalinity, pH and calcium, or at least keep them fairly regular. If its a big enough tank, a lil bit of chlorine from tap water isn't going to drastically mess anything up. I would imagine there's some sort of macro algae somewhere in the reef tank as well if it is handling removal of nitrates.

 

[chrisnif]

I dont think there is macro, but there is plenty of coraline and the walls are covered in green hair, which frankly doesnt look that bad fully covering

 

[socalnano24]

green hair algae will pull alot of bad nutrients like phosphate and nitrates out of the water.... that'll do it. Have you ever seen that thread floating around about the algae scrubber bucket fliter? (that uses "turf" algae under controlled circumstances for the same purpose)

 

[chrisnif]

Yeah I was thinking about building one of those Just think it'd be awesome to go a day, let alone years without getting wet

 

[stanlalee]

how dense is the coral growth? how much water volume total? how is growth of these corals? how long as he been taking this aproach (perhaps never means he started this 2 weeks ago)
a. large water volume to coral density is usually going to deplete of ca, alk slower
b. aragonite (crush coral, live rock ect) does NOT buffer ca and alk. it does not dissolve at anywhere near tank water pH which is why ca reactors use co2 to drop pH in the 6's to dissolve it for buffering ca and alk. certaintly wont be buffering at a pH of 8.3 given.
c. growth has to be stunted if as described. corals consume ca and especially carbonates (alk) for growth. no way around it. there is no way alk and ca dont deplete with proper growth. I would expect a tank many years old that size to have its acro's sticking out the water, montiporas huge scrollers with fragging corals a neccessity to impede infringement on each other. anytime you can get away with no calcium and carbonate supplemeting on a tank sized where dumping daily 500ml bottles just to maintain those levels is normal things may be living fine but they certaintly arent growing like should.
d. he could have not told you EVERYTHING. perhaps he forgot to menton dosing ca and alk or a calcium reactor. maybe he just adds water with kalk and forgot to add that little bit (although that would still be insufficient for proper growth on a reef tank up that long).
e. is this tank plumbed in to other systems/tanks in the store?
f. how long as this approach been successful?

 

[socalnano24]

Ok. Good to know on the calcium ph. I know I did read somewhere about alk buffeting from a deep bed of crush coral or arg sand. I'll have to look it up at home.

 

[chrisnif]

ITs 8 feet x 2 feet by at least 2 feet so somewhere in the 200-275 gallon range depending on height. It has a bunch of softies, the montipora is on the back wall and its "discs" are dinner plate all the way down to 1/2 inch, its grown up the back wall, and all the way to the front wall. The Acropora is probably 2 feet wide, 16 front to back and probably half the height of the tank, its at the surface but I dont think it will grow out of the water, seems to be growing "out" more than "up" Who knows its still either way an awesome tank for very little work even if he is adding stuff to makeup water.