Backyard Aquaponics
A place to discuss aquaponics

Scenario:
We have had a bit of rain which has increased my fishtank volume by about 15% as the gh is yet to be covered. I have noticed since that when fishtank pump cuts out, all gb taps continue to siphon slightly at this new higher fishtank volume. (Was wondering why my sump pump was kicking in at odd times when i don't pump o'night.) Opening the return ball valve to the fishtank at the end of the day's pumping, breaks the siphon completely, until pumping resumes next morning.(The fact that this slow dribble causes one or two sump cycles o'night is in fact a good thing with regard to aeration i feel.)

Question: Is it possible I had an anoxic environment in the bottom of my gbs, causing nitrate offgassing, when my gb taps were not quite cutting out? This meant there was always a little water in the bottom of the gbs, covering the gravel that could host anaerobic bacteria.

I would be interested in replies for this reason:

I have lotsa tiny fish, therefor a small fish load in total. Have added rock from previous system so things are cycled already. I don't want nitrate offgassing at this stage, bc I am not producing much for plants anyway. 6 months, yeah sure, but now I need nitrate,(she is starting to look sideways at me again!) By the way readings for nitrite is next to nothing and I have not recorded nitrate at all in this new system.

Sorry for the long wind post, needed to paint the picture and await replies.

It is quite possible TT. Quite seperate to the anaerobic stuff that we are talking about here, if you look at the Koi forums and stuff - there are other types of filters that gas off nitrate (can't remember what they are called) which are not that dissimilar to some of the action that is caused by F&D in gravel beds. I suspect that any F&D setup will gas off some nitrate due to anaerobic as well as the GB action.

While the missus is not looking at you sideways - you may want to PM me to find out some more about how you can use urine to solve your problem

Right on the money, VB. I agree.

I don't think you would be able to completely stop offgassing regardless.

thank you both for prompt replies.

Still on the topic of having my pump mostly off at night, what if I stuck the RSG filter into the fishtankwith the top just above the water level. I could take a T off of my main pipe and deliver water to the RSG when the pump is on. When the pump is off the filter will be mostly submerged and therefore not let any air in. ???

That sounds promising, KE. Go for it.

My RSG has been going for well over a month now - guess I shoul pull my finger out and take some readings to see if the nitrate is any lower. Maybe tomorrow (where's my beer ).

looks like all of us brisbane people think alike. I started an RSG last weekend on the tank that houses my new SP, don;t have a test kit so will still do regular water changes but will arrange one once I get some cash and then all of us can compare notes.
will post piccies once I get them.

I now have enough plant mass that I am able to go without an RSG filter. My nitrate is holding between 5 and 20. I left the PVC in place and just backfilled with gravel so that I can refill with sand if nitrates start getting out of hand again.

Glad to see more people trying RSG filters so we have more data points.

Nick - your system would still be cycled wouldn't it. Re: the water changes, is it just the nitrates you are worried about? I wouldn't think you would have much problems there if you are pushing the water through a planted bed. How have you set up your nursery?

I have just bought a new kit because I was very low on ammonia test (virtually all gone) and getting close to finishing the nitrate (though quite a few tests left I suspect). Hepas of nitrite, and ph left. If you want my old one to tide you over - let me know.

I just bought replacement nitrate tester when it ran out (cheap skate )

Will be monitoring my RSG filter setup regularly now that I have the fingerling tank connected to it - reports to follow

Only reason I bought full kit was that the ammonia and nitrate are low and is nearly same price to buy the whole kit as those 2 lots.

the nursery is not set up with a growbed. it is just the tank and a normal filter, so the nitrates will be building and keen to not waste water.

Can you move the water between the nursery and a tank cycling through the grow-beds Nick?

BTW - I've got a similar thing happening (ie nursery just has a bio-filter). I've not had to do much in the way of water changes in the 3 or 4 weeks since getting Barra. Probably only 100 or so litres.