Autoclaved Aerated Concrete (AAC) as a DIY Live Rock

[Pavle Novičić]

Hello everyone,

I am new on this forum and I just wanted to share with you an experiment that I started few weeks ago. The idea is to take regular AAC ( for building), cure and shape it to look like died out coral, and put it in the reef tank. It could be also used as a filter media in the sump, to reduce the amount of rock that will be put in the display tank. As it would be too much risk to put a building material in the already formed aquarium, I decided to start a new one, and measure its progress using pro test kits and national lab for measuring presence of Aluminium, which is added to the mix when the block is formed, in the water. I searched everywhere and I just couldn't find that someone had been tried it, but because of its characeristic it seems as a perfect DIY live rock. Its porous surface would provide enough space for benefitial bacteria to grow, its lightweight, etc. The problem is chemistry, and question is will it, once soaked in water, leach something in it. The experiment is supported by the leading Serbian reef aquarist ( and his company ReefrooM), and many people is following the progress every day. This type of DIY rock would have a lot of advantages to the previously created 'custom rocks'. First of all, the material itself is very cheap, meaning that for under 20 EUR ( 30 USD) you can fill 55gal (200l) tank with rock. You all know how much it would cost with regular LR. It is easier to create than DIY rocks made of concrete with oyster shells or salts. And the best thing of all is that you can shape it to whatever shape you want in the metter of hours, whithout too much effort. You only need a sharp tool and and a bit of creativity.

I am not going to write too many details now, but if you are interested in this project I will be glad to share more details, photos, test results and overall progress of the tank. Here is the photo with soft coral doing just fine in the test tank.

Cheers!

[Deleted User 8]

Of course we are interested! Post away!

 

One bit of feedback, the holes look too uniform to my eye. It looks like you used the same tool to make them all. IMO, it would look more natural with varying size holes and a bit more solid rock space (less holes). That is just looks, I am more interested in the stability of the cured rock regards leaching anything bad into the tank. Phosphates, heavy metals, etc. This is a great web page that has some good info: http://delreefclub.org/index.php?Itemid=1&id=27&option=com_content&task=view

 

Welcome to the forum!

 

Buzz

[Pavle Novičić]

I couldnt agree more with you. It could look better but it is made just for test. Improving shaping skills wouldnt be problem later. Phosphates are ok measuring 0.36 after 50 days without waterchange. It is probably due to feeding the empty tank to start the cycling process. I ve added a way to much fish food. After a major waterchange they measure 0. The main concern is Al present in the block. As soon as it is highly toxic to the aquatic animals, we paid a great attention to it. We tested it in lab that tests drinking water in our country, so that we could be 100% sure it is safe.

[Deleted User 8]

Yes, sure--you can shape it in many, many ways. That is pat of the draw to DIY rock. I would like to make an arch with some rebar inside. Make iit all one continuous piece with nice flat bottoms. Yup.

 

I would place the new set rock into some fresh RO/DI water with a pump to circulate. Keep it dark. Then do some testing over time and see what you get.

 

Keep us posted and thanks for landing here!

 

Buzz

[Pavle Novičić]

Making an arch with AAC is very simple. You wouldnt actualy need a rebar, as long as you are not planing to build an arch 3ft long.

We sat down and discussed the best way, and agreed that theres no better indicator than corals, starfish, snails, fish, worms, etc. They will tell us over time how happy they are with AAC.

In the next few days I will write down everything from the beginning, what we went trough and that sort of stuff. Hope it may help someone in the future!

[CronicReefer]

I'm sure this project will work out great. There is a company here in Florida that makes concrete structures that are used to help create and restore reefs in the ocean. I'm sure we can do something similar in our aquariums and I like the idea of being able to mold your landscape

[Pavle Novičić]

The problem is that manufacturer, in my case YTONG, does not suggest using those blocks for anything else but building. It is not meant in water. It will not harm people, plants and animals as long as it is used for its purpose. This still doesnt mean that we cant use it, and I do believe that it can work. Although I ve been working on this experiment for almost half a year, still cant conclude anything. As I previously mentioned my biggest concern is the presence of Al powder in the mix for making block, which could possibly leach in the water making it highly toxic. After soaking the concrete in water for 60 days I took the water sample and took it for testing, and results showed no presence of Al. Those were good results for a start.

When people are talking about water quality in their reef tanks there is lot of chemistry involved, and unfortunately I am not good at it. God knows what else can this block leach in, and contaminate the water, so it would be too much effort, time, ( and money) spent for analysing everything. Instead of that, we decided to add low demanding organisms, and slowly make our way towards more demanding organisms such as SPS corals. For the experiment we are using 30l ( about 9 gal) glass tank, powerhead (650l/h), 25 w heater, 24w combo acintic blue and 10 000k white fluorescent tube and about 3kg of live AAC rock. So far, all the organisms added are doing really well. In few weeks we will add some more sensitive corals, so I will make an update to let you know how well they are doing.

Cheers!

[CronicReefer]

Try adding a clove polyp colony. I believe mine died due to Al leaching into the water from the phosphate absorber I was using. I have heard that clove polyps are sensitive to even undetectable amounts.

[Pavle Novičić]

I will but I do not believe that there is undetectable amount if you test it right. There is Al present in the tap water, ocean, rivers, lakes, everywhere. Thank you for telling us particular corals we should try. Can you give me more details or link where I could find the Po4 absorber you were using?

[Horerczy]

Hmmm. Something like a mantis shrimp would be good to testy with that. See if the mantis tunneling into the rock releases any undesirable stuff into the water column

[CronicReefer]

I will but I do not believe that there is undetectable amount if you test it right. There is Al present in the tap water, ocean, rivers, lakes, everywhere. Thank you for telling us particular corals we should try. Can you give me more details or link where I could find the Po4 absorber you were using?

I was using phosgaurd but I believe any aluminum oxide phosphate absorber could cause the problem I had with my clove polyps. When I added phosgaurd my clove polyp colony slowly turned brown and died off from 20 healthy polyps to 0. My second colony was doing the same so I stopped using phosgaurd for a while and the brown receded and they started growing back. Now that I'm back to using a different aluminum oxide phosphate absorber I am seeing the same symptoms.

[Pavle Novičić]

So, yes it would be safe to say that Al oxide phosphate absorbers are not safe for some corals. As Al is also used for making bubbles in the AAC concrete, the same thing would probably happen in my tank. Still it doesnt mean that AAC could not be used. Your personal choice was to grow the particular coral and remove the absorber out of the tank. That is what you've done. On the other hand, you could choose not to grow that coral and substitute it with one that can live in conditions like that. Dont know much about your tank but guess that other corals were doing fine, or I am wrong?

 

Hmmm. Something like a mantis shrimp would be good to testy with that. See if the mantis tunneling into the rock releases any undesirable stuff into the water column

I believe so, and will try with that, thanks.

[Pavle Novičić]

The main point of AAC LR is incorporating it into the concept of low-budget reef tanks. When I say low budget reef tank I am not talking about low budgets you can see on Youtube, or forums. In these videos people are showing bunch of equipment including LEDs, skimmers, auto top offs, sumps, etc. I mean, guy finds 50 bucks cheaper lights somewhere and he makes a video about low cost aquarium light. In Serbia, previously mentioned leading reef aquarist, set up 3 aquariums using only powerhead( or streams, wavemakers) heater, water, live rock and T5 lights. No skimmers, no sumps, NO TESTKITS. Just lights and regular waterchanges. I will put link here, I know that you cant understand, but you can look at the photos and see what man has achieved over the year or so.

http://www.akvarijum.org/forum/low-budget-60l-t12782.html

Of course, not all corals will survive in this conditions, but it is still beautiful and colorful reef. So the idea is to substitute the real LR with AAC and you get good looking aquarium very cheap.

[Deleted User 8]

IMO, conducting your research by using various animals as test subjects to see what happens is not very scientific. There are just too many variables and subjective inferences involved. Not to mention is sucks for whatever you plunk in the tank if there really is an issue with the concrete leaching deadly things.

 

Again, IMO you would get better data if you reduced as many variables as possible and would run comprehensive chemical assays on the water used with the concrete. It would be far easier as well and cheaper too. Set up some trash cans with various chunks of the stuff, large to small (use a hammer instead of a mantis to crush your rock into smaller bits!).

 

Buzz

[CronicReefer]

So, yes it would be safe to say that Al oxide phosphate absorbers are not safe for some corals. As Al is also used for making bubbles in the AAC concrete, the same thing would probably happen in my tank. Still it doesnt mean that AAC could not be used. Your personal choice was to grow the particular coral and remove the absorber out of the tank. That is what you've done. On the other hand, you could choose not to grow that coral and substitute it with one that can live in conditions like that. Dont know much about your tank but guess that other corals were doing fine, or I am wrong?

I believe so, and will try with that, thanks.

Yes only the clove polyps were affected. All my other corals show no signs of any issue with water quality. I don't mind not being able to grow cloves but I would like to see a third party verify Seachems claims that at higher pH levels the Al from Phosgaurd does not leach into the water.

[Pavle Novičić]

IMO, conducting your research by using various animals as test subjects to see what happens is not very scientific. There are just too many variables and subjective inferences involved. Not to mention is sucks for whatever you plunk in the tank if there really is an issue with the concrete leaching deadly things.

 

Again, IMO you would get better data if you reduced as many variables as possible and would run comprehensive chemical assays on the water used with the concrete. It would be far easier as well and cheaper too. Set up some trash cans with various chunks of the stuff, large to small (use a hammer instead of a mantis to crush your rock into smaller bits!).

 

Buzz

 

Well this cant be called scientific research for many reasons. First of all, to call it scientific I would need as many experts as there are different fields involved. I would need marine biologist first and many lab experts to carry out complex chemical analysis of the water. You probably know that analysing saltwater is far more complex than analysing freshwater and requires really sophisticated and expensive equipment. I do not personaly know any marine biologist, Serbia doesnt have sea, so I dont think I will soon meet one here. Testing water is expensive, so I cant do it every day, still I tested Al levels, and they are not even close to what is considered toxic for people. I also lowered ph levels in the water assuming that will cause leaching of Al. Still no Al.

Having mentioned all that I can only rely on the experience and texts on forums. If the fish and corals survive in my tank I think that will be enough to prove that AAC can be safely used in reef tanks.

[Deleted User 8]

If the fish and corals survive in my tank I think that will be enough to prove that AAC can be safely used in reef tanks.

 

I disagree. It would prove little else other than it "works" for you and your specific tank. Oh, and scientists are not required in scientific research!

 

I think perhaps it is not such a big issue really. From: http://www.aluminiumdesign.net/design-support/aluminium-corrosion-resistance/#toc-aluminium-in-soil

 

"Aluminium corrosion resistance is very good in untreated aluminium. Untreated aluminium has very good corrosion resistance in most environments. This is primarily because aluminium spontaneously forms a thin but effective oxide layer that prevents further oxidation.

Aluminium oxide is impermeable and, unlike the oxide layers on many other metals, it adheres strongly to the parent metal. If damaged mechanically, aluminium’s oxide layer repairs itself immediately.

 

This oxide layer is one of the main reasons for aluminium’s good corrosion properties. The layer is stable in the general pH range 4 – 9."

 

Buzz

[Pavle Novičić]

Can you tell me one reason why it wouldt work in the similar conditions in any other tank? Here we are talking about controled environment, where everything is measured, ph, salinity, temperature, mg, kh, ca, no3 and po4. I dont see any reason why it wouldnt also work in tank with similar parameters, which are considered normal for reef tank. If you make a mistake or have any other problem AAC is not to blame. Our goal is to prove that AAC can work. I thought that ca levels will rise and lead to calcification on the equipment. It wasnt the case. Still everything works.

Perhaps scientists are not needed, but I am far from scientist. I study Japanese language and literature, so my research cant be called scientific Just testing.

[Deleted User 8]

Well, once you have a bunch of livestock in the tank, they will effect those things you are testing for. They could be contributing to high levels of something like ammonia or they could be depleting others like PO4. It really is quite far from a controlled environment. Also, if something dies or does not thrive in your tank, there is really no way of knowing if the rock was to blame. Too many variables.

 

If all you have in the test tank is the rock and water, those test results can be more clearly associated with just the rock (assuming pure saltwater or RODI).

 

Again, I am thinking that there isn't much to worry about, at least concerning aluminum. I'd be more interested in PO4 levels.

 

To clarify, the AAC is only available in blocks that need to be worked into rock shapes, correct? It is not something that is formed wet by the end user.

 

Buzz

 

[Pavle Novičić]

How could we monitor po4 levels if there was nothing to create it? AAC cant produce any po4. Thats why we have added livestock. We started experiment in June, and first animals were added in October. So this can be considered second phase of the experiment. In the first phase of the test we did almost exactly what you are suggesting. So now we want to see how it works in practice.

Yes, AAC comes in blocks that need to be shaped, but it is not hard to do.

[Pavle Novičić]

New corals added last night, light changed to 3x3w LEDs, white 10000k and 2x blue. Here are pictures. Sorry fot the quality, but smartphone I am taking pictures with cant do any better with leds on.

[CronicReefer]

Just to show you that reefs can be made using concrete, the Reef Ball.

[Pavle Novičić]

Yes, I know. But in our small tanks its a bit more complicated. To mess the chemistry of any sea or ocean you need a ship full of oil. Just few concrete blocks cant change a thing. But in small tank it can.

[Horerczy]

AAC is by my research into a few datasheets is insoluble and chemically stable so i doubt there well be any issues at all.

[Pavle Novičić]

Me too