Backyard Aquaponics
A place to discuss aquaponics

Could be, but am not concerned that it be in this range because it is well within what Tilapia will stand but I am wondering if I should be concerned about the level changes. Not sure what Lava rock will do to ph but really did not notice any difference when I added the other growbed. What is perplexing is that it does go down.

Should I not be more concerned about nitrates than fluctuations in PH? especially if the fluctuation is only < 1ph?

I am hoping the added vegetation will bring the nitrates down. I also planted 20 tomato seeds, some basil, some chives and more milo to see if I can't control it. I am probably over doing it and will have to either pull plants (which I can) or buy more fish. I want to work up to 7Kg of fish eventually anyway as GB allows.

Hi DT, It's looking lovely!

Concrete has a very high pH, but since you have the inside of the tank sealed, I wouldn't think that would affect it....unless the sealing is old and cracking. Folks here run with some fairly high nitrates (maybe even over 100?), so I wouldn't be concerned about 20-40. Your plants need something to nourish them, after all. Your nitrite (and presumably your ammonia) are not reading, so you have cycled. More vegetation will slowly bring your nitrate down. I think it's a little strange that you say you get fluctuations on that reading. I would actually stop with the water changes and see if that doesn't even out the fluctuations in pH.

DT, re your water lettuce, it looks a bit like our native (to the Northern Territory) water lettuce, Pistia stratiotes.
This plant is a declared weed in New South Wales and a problem here in Queensland.
Try looking up Pistia sp. to see if you have a local one in Central America.

You also have Lemna sp. duckweed in the tank. Good for the fish.

Oh, hang on. Here is some wiki info on it, different from my text book.

I can't see anything about fish eating the water lettuce. The water lettuce shouldn't be a problem unless it is set free.

I don't set anything free. All things will go out via the table or the compost heap. In actuality I got it from the wild so I don't think it is a problem here.

When we see weeds we don't like here, we say, "Well, I declare!" That is how we declare them weeds here

So I should not be worried/concerned so much about fluctuations in ph? I will hod off on further water changes.

I just got back from talking to a carpenter about building my grow beds. It looks like I will be using wood. I will then put a thick plastic liner in ithe trough to make the GB. Not optimum but what I can afford and what I want to build in a house I am renting.

I went to the volcano again yesterday and got a pickup truck load of lava rock. I will have it sifted and classified tomorrow. Hopefully for Christmas I will have some semblance of a new Growbed. The view at the volcano was spectacular. My son is a photographer and he shot a bunch of pics so if it is OK I will post some so you can see what I have to suffer through to get decent gravel.

Growbed media in its virgin state post...post...post

Well DT, pH fluctuations have to be caused by something, and I would be a little concerned about them, but only so far as you can actually do something about them. My best theory is that your water changes are causing the fluctuations. That is something you can control. If it is a daily swing, there is less that you can do about it, although adding buffering may help lessen the swing. This is where we hope STEVE has some words of advice.

yeah, I was hoping he wuld weigh in. In one of the threads EB mentioned using shells to raise ph and wood to lower. I would be interested in knowing more about using wood too lower ph.

I added 2 lbs of aquarium salt to 600 gallons and it did seem to make for happier fish but didn't do much to either soften the water or change ph. Later, I read that by adding salt, I may have actually raised the ph.

While at the lake yesterday, I took a water sample and it was about 7.8. There is a huge population of tilapia in that lake that grow wild so my ph is not that far off from that. So..... I am almost ofthe opinion that I need to leave things alone and let them work themselves out.

Wood will lower pH as it decays. Your setup's pH will gradually drop as it matures, simply because organics build up and decay. I never found that wood did a lot to lower pH, but I also only used a limited amount to keep the plecostamus happy.



I agree.

Dt your system will handle much higher nitrates than that. More nitrates = more plant growth. More poo is good!!!

Okay I will leave enough alone for now and just keep adding plants to take advantage of the nitrates.

Next question:

When I get the new grow bed, I would like to use the lava in the present grow beds to kick start bacterial growth. What would be the best way of efficiently doing this since the lavain the current growbeds will nowhere near fill the new growbed? I was thinking put the old lava under the new lava so it would get more moisture and spread through the rest of the lava.

Or should I spread the old lava on top of the new lava so bacteria will soak down through it. and cause growth in that way. I plan to vacuum poo from the bottom of the fish tank over the growbeds tohelp in the process and I will leave one of the growbeds active so that something growing will keep using up the nutrients produced by the fish. I expect this to happen in the next couple of weeks as I don't think I will get the GB made before christmas. Would it help to put a couple of buckets of lava down in the fish tank to get a film on it?

The bacteria would prefer to be protected from extended periods of light. I think it would be best to spread innoculated rock in the bottom of the new bed, then cover it with un-innoculated rock. Don't let the innoculated rock dry out, or remain in the sun for long. Water circulation will also spread the bacteria from wherever it is, to wherever it is not.

Thanks, I will keep that in mind.

DT, been busy, sorry

Regarding PH, what time frame is the swing over? morning to night?

20-40 nitrate is probably ideal! Don't touch!

wood lowers the PH as (i think) it releases humic and tannic acids.

In a functioning system ph will always drift down due to the acids release as part of the ntrogen cycle.

If you PH is up and down by about a point between day and night then i think its probably just any algae (if you have any). There is a word for it, can't remember it now, is often seen in marine tanks with sea weed. Happends due to co2 removal during the day (ph up) from water plants