A number of points:
Ski- as much as I’d like to take credit the tanks not mine I’m afraid. Its one of Takashi Amano’s creations, if you google him there are lots of pictures of his tanks on the web. If you really like your fish then I would advise to invest in his books ‘Nature Aquarium World 1-3’ they are amazing.
Dan1980 – A high bioload will reduce pH – this is due to the build up of tannic and humic acids associated with the breakdown of the plant material found in the tank and in fish food (its about 50-60% in most commercial feeds). Carbonic acid has a lesser effect as it dissocates to C02 and OH- very quickly. Also when water hasn’t been changed in a closed system the mineral content, which provides the buffering capacity of the water, decreases therefore allowing greater fluctuations in pH to take place. The overall effect is to decrease the pH.
Also all aquariums contain anaerobic bacteria as most of the bacteria in the tank as facultative – i.e. they can use oxygen or not depending on the conditions. Denitrifying bacteria however are obligate anaerobes which is why deep sand beds/plenums/live rock are used in marine systems as the bacteria won’t tolerate any oxygen. Also the biofilms that develop on all aqurium surfaces (including the glass)can be comparatively thick (100 micron plus) and due to the oxygen demand of the surrounding bacteria can result in a large number of anaerobes being present. In reality the build up of hydrogen sulphide is very rare in home aquariums as it would require such slovenly fishkeeping that the fish would die long before gas became a problem.
Aerating water before a water change is nothing to do with C02 more to dissapate free chlorine in the tapwater supply. Water conditioners remove this and to a certain extent chelate copper – free chlorine is highly reactive and unstable so approx 90% is disocciated within the first hour of aeration. The remaining 10% takes a further 12-24hours (again its a log scale). Copper isn’t a big problem in freshwater tanks unless the OP wants to keep lots of shrimp.
You are right though the OP should find out the nitrate levels of the incomming water as its not a lot of use constantly changing water if its all 50ppm +
🙂

most of the bacteria in the tank as facultative – i.e. they can use oxygen or not depending on the conditions.

I was pretty certain that was the case but when I went to double check I couldn’t find any references…….thanks for confirming.

That’s why after any serious canister filter failure/malfunction I have always let the outlet run into buckets when starting up again, to flush out the contents, before returning the outlet back into the aquarium.

Yep spot on Ernie – though you have made me realise that I made a spelling mistake in that post though 😀

No wait magowen …….just figured this out : “Denitrifying bacteria however are obligate anaerobes”

😕 Why ?

Now I understand the theory behind trickle filters, but surely the theory behind high volume/turn over, of undergravel filters is to provide the environment for obligate aerobe bacteria ?

The ammonia reducing bacteria in filters are mainly aerobes hence the need for water flow (or more specifically oxygen).
Denitrifying bacteria are those that use nitrate as a food source and are obligate anaerobes. This is the thinking behind deep sand beds/plenums in marine set ups – the upper layers of the sand hold the Nitrosomas and Nitrobacter that reduce ammonia the deeper layers hold the chemotrophic anaerobes (genus name escapes me) to keep nitrate levels under control.
Simples!
😀

Right sorted, so the deep bed set ups act like trickle filters too – as well as in the conventional high turnover undergravel system ? Ta magowen 8)

A huge thanks again guys – did everything as described and nitrate levels are now extremely low and everything else is fine

Off to get some more fish this weekend and do my water changes and checks as described

Really great advice

Ta

Ernie – not sure on your meaning of the last post. Trickle filters don’t denitrify (if anything the opposite). Oxygen exchange is at its greatest at the water/air interface so the thinking behind trickle filters is to maximise ammonia reduction by providing more oxygen. Nitrate is very difficult to remove from any closed aquarium system hence the need for water changes. The best thing you can actually do to remove nitrates is use house plants sat in pots above the tank – the roots will grow down into the water and use the nitrate as a food source (as a side benefit they’ll also use water so you have to regularly top up, therefore changing more water).
Tankslapper – I don’t want to sound patronising but presonally I’d advise leaving things to settle for another week before adding more fish. Don’t get me wrong you could and it’ll be fine but it would be like going out for an enduro ride after the longest cold in history. If you absolutley have to get some fish only get 1 or 2 and build up slowly. My personal rule of thumb was no more than one fish a week. Glad to hear things look better 🙂

Trickle filters don’t denitrify (if anything the opposite). Oxygen exchange is at its greatest at the water/air interface so the thinking behind trickle filters is to maximise ammonia reduction by providing more oxygen.

Sorry I wasn’t talking about wet/dry trickle filters. I’m talking about totally wet trickle filters which work on the basis that the media (often sand) is totally submerged and the water passes through sufficiently slowly enough for denitrifying bacteria.

EDIT : I’ve just checked and apparently wet trickle filters were discredited in the mid-nineties ………….it’s been a while since I’ve set up a new aquarium and therefore I am obviously not up to date with the latest fashions ! I guess it’s a bit like if you don’t buy a new bike for 15 years 😀

Anyhow, in case you’re interested :

Denitrifiers
For a short time in the early to mid 90’s there were advertised a lot of different kinds of denitriying filters. But you don’t see them much anymore because they don’t work. That sort of put a damper on their sales.

Anyway, this is how they are supposed to work. Nitrate can be used by anaerobic bacteria as an oxidizer instead of oxygen. In effect, the bacteria breathe nitrate instead of oxygen. So if you create a region where there is no oxygen, but lots of nitrate, and a food source for the bacteria in the form of a carbohydrate, then the bacteria will consume the nitrate. The end result is nitrous oxide or nitrogen gas, which diffuses out of the water into air.

In denitrifying filters water is very slowly passed through a submerged filter medium. A small amount of a sugar (bacteria-food) is added. Aerobic bacteria consume all the oxygen in the outer layers of the filter medium, and so bacteria in the inner filter consume the nitrate in order to metabolize the remaining sugar. By the time the water passes through the filter, it has had all of the sugar and oxygen consumed, as well as at least some of the nitrate. The water is then aerated to replace the lost oxygen and get rid of the excess nitrogen gas. It is then returned to the tank.

So, why don’t they work? Well, in practice, they are just too touchy. Too much organic matter in the water and you get poisonous hydrogen sulfide being produced. Pass the water through too quickly and ammonia is produced. Etc., etc. And even if you do get them set right, you must pass the water through them so slowly that they do not produce enough nitrate-free water to make any real difference to your tank, unless you get a very big denitrification filter. That means big bucks.

and in closing…

Tankslapper – roughly where abouts in the country do you live?

I’ve worked in the industry for 15 years and know which are the best stores to use.

Ahh – crossed wires – understand what you mean now. Admitedly I’m a bit out of touch with the latest tech in fishkeeping as I’ve been in research for the last 7 years and was never a home aquarist.
Its interesting to read that article though as personally I always thought denitrifiers were a bit duff for home aquaria. By that I mean that if you need to keep your water quality acceptable through chemical means you can’t be on top of your husbandry. Denitrifiers do have uses in commercial applications though.

John

Welshpool if that’s any use

cheers
TS

Not really, I’ll make a couple of calls this morning and post up later for you.

$hit, I was so busy today I forgot to make those calls for you. Sorry.