Backyard Aquaponics
A place to discuss aquaponics

Hey Steve

Did a water change Wednesday, fish wearnt eating much, and hiding a lot.

Got my heaters on Thursday, put one in and watched the fish swim around it while it warmed the water up, 22C and they are quiet active, and feeding up the top, puting a pinch in, and none of it hits the bottom.

They seem a lot happier at this temperature.

Was out riding the bikes with my kids and noticed 2 old baths in a back yard, may go around and ask if they want to get rid of them - they might make good beds.

Warren

An update regarding the stainless steel tanks:

I have gone off them a bit. The tank maker says that they are corrosion free and will last 40 years. Problem is that all stainless steel is subject to corrosion - it just depends upon the environment in which it is in and the grade of stainless steel. We all know this from the fact that saucepans, sinks, dog bowls and otehr stainless steel prodicts we have had have at some time had corrosion issues.

The tanks are 304 stainless, which is a pretty good grade, but they are subject to corrosion under certain circumstances, a major one being when there is chloride present.

A quote regarding 304:

"Corrosion Resistance
Excellent in a wide range of atmospheric environments and many corrosive media. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Considered resistant to potable water with up to about 200mg/L chlorides at ambient temperatures, reducing to about 150mg/L at 60°C."

In accordance with this, it would be necessary to ensure that the chloride levels are always lower than 200mg/l and the lower the better to be safe.

Tis would mean that using salt as a medication would be a definite no no as the levels you would want are higher than 200mg/l (Steve, feel free to correct me if I am wrong).

Also, it is probably a little questionable what the other impurities caused by the fish growing might do to the stainless.

Anyway I am not totally off the idea of these tanks, but it is looking like I am heading away from them. Does anybody have any knowledge or opinion about this.

PS - I definitelly won't be getting my 5000 gallon stainless rainwater tank now as the site for the tank is behind my swimming pool and I expect that would result in exposure to chlorides - from the chlorine in the pool.

VB,
Stainless 304 grade is used a lot in boat building, ie hand rails and screws etc and it does corrode in a salt environment. Surface rust staining will appear fairly quickly but can be (in the case of boats) buffed off without much effort.
Stainless screws used are mostly 304 because 316 screws etc are better for corrosion but are much softer therefore not as strong and easier to break or strip the slot in the head when inserting....like everything the use of stainless is a trade off between various factors. 304 stainless screws corrode out fairly quickly actually especially in the presence of some other metal especially aluminum.

I also wonder about the electrolysis effect of a stainless tank with just enough salt content and an alloy bodied pump immersed in the fish tank. I reckon you would have all the same problems the boating world has, one or the other would corrode very quickly (maybe) May need some Zink anodes.... but then there is not much salt present so the effect would be minimal.

316 grade stainless is much more expensive to buy than 304.

I must admit I did not think about the addition of salt to the fish tank even though I have been adding small amounts to my tank every time I have a small water change........... really, the amount of salt is pretty small.

I think you have picked it pretty well......Stainless unbeatable in the case of a house rainwater tank, but (I know I am biased) in the long run a good FG fish tank is going to be unbeatable... in 15 years it will still be giving good service with very little difference since new, maybe a few scratches and some stains, but that will be it.. no degrading or breakdown
Murray

Yeh I'd still like to get the stainless rainwater tank, but by far the best location for it is below my pool area. I will have to give it some more thought regarding how to stop any pool overflow etc getting near the tank. In my case it may be a safer bet to just go for the poly.

Re: the salt content in the fish tank, when medicating fish with salt the doses are pretty high. Though having said that it may not be plausable in such a big tank to dose at this rate anyway (its a lot of salt).

Re: the reaction between pump metal and the stainless, wouldn't this only be a problem if the 2 were touching. It wouldn't be too hard to stop them from touching. Besides which I am now looking towards a pump that does not have a metal cover (see flood and drain etc thread). [I hope I am not starting to talk myself back into a stainless fish tank ]

Re: Fish tank - looks like a Murray built FG tank is back on the cards, unless I just decide to settle for poly.

In a way it is good that I am ruling the stainless out, because under this option I was moving towards getting the fish tank much sooner than intended originally (due to getting at the same time as my rainwater tank). It has always been my intention to run a test setup first with single fg growbed and my little poly ponds as fish tank. Will go back to this plan, which will also give me time to plan and build the greenhouse.

VB,

salt level i quoted to murray for nitrite protection.

Few few observations. I'd only use that level of salt if i was setting up a new system and absolutely HAD to get fish in there. ie max protection from a very young system.

salt medication for parasites would go far above this probably in the range of 4000mg/l besides you'd need to chuck a 20kg bag in for this (i picked that figure out of the air )

But exposure would only be for about a week

Man i gotta stop here, just realsied that this can get very messy with numbers. Salt water has 35,000ppm sodium chloride, which equates to a chloride level of about 19,000ppm. See where the confusion comes in?

End of the day VB, you'd be putting in for nitrite protection (just cycle your system slowly and properly instead). This is getting way too comlicated, you know what i'd do if i was keen on a 304s/s tank? i get a 10cm square sheet and pop it onto a brick at the bottom of my pond system for a year Hard emperical evidence straight from the system. pull it out after a year and make a judgement call Besides i'm sure we will all have multiple systems like joel one just isn't enough just leave the killer stainless stell one to last

EB,

How are you finding your bulka bin tank?

do you think the 2000 X 480 pond i found would be better/worse/indifferent from a fish point of view?

Steve

You should ask the fish........

Ummm, guess I may not have read the post yet where you found a pond and you only give 2 dimensions, how deep is it? My bulka bin is doing ok at the moment though I only have one silver perch and about 30 goldfish in it at the moment, gunna be time to stock it up soon, then I'll find out for sure how they go in there.

Hi guys:
What does a bulka bin look like? I Googled it and didn't find any images.

Dave , its those whate 1M cube plastic tubs in a mesh cage used for liquids transport.

EB, Ha! Tricked ya , you only need two dimensions if is circular

Back to the bulka bins - where does a person get their hands on something like that?

Recycling yards have them, they are getting quite common down here due to the water restrictions. current prices seem to be about $100 to $130, they hold 1000L in a 1M footprint, dare i suggest look on ebay?

Steve

Only a bulka bag, nothing like you have described... 2 bulka bins would do me fine, but I would want to connect them somehow...

sorry AM, i started using that term after EB used it, i've not actually seen them called that on ebay. Just do a search under water storage.

here is an example
http://cgi.ebay.com.au/Water-Storage-Ta ... dZViewItem

thanks- but the postage 5to Cairns from that supplier would not make it worth it... pitty, but now I know what to look for!

Nah, no way was i suggesting buy from that guy and ship it! Just so you know what to look out for. Are there any good recycling yards or secondhand building material places around you?