Nexus air solutions?

[Chagoiboy]

My nexus 300 (pump fed) which ive had for 4 years doesnt seem to be turning over too well nowdays. Airpump seems ok (airtech 80, old style). A lot of the K1 seems to be sitting at the bottom! (i thought it floated..) and not getting tumbled. Ive cleaned the holes out a few times and enlarged them a bit last time and added a few more near the outlet where i was getting some bunching, maybe ive overdone the holes now? diaphragms are fine.
It does tumble but you can see its not all of it tumbling..

Anyway, remember reading of a few people who replaced the air ring with airstones etc to good effect, anyone have any details please?
Thanks.

[Casper Chapman]

When this happened to my 300 it was because of crud build up below the air ring, so you may need to remove all K1 and clean out the complete unit.

[brians]

i put an air ring of 22mm john guest pipe round the top outside rim of my nexus 200 in a sort of horshoe shape ( the open part of the horseshoe being where the inlet is, i then drilled 6 holes in the 22mm pipe and fitted smal airtaps (like what is on an airpump manifold) and connect flexible airpipe and airstones to this this turns the k1 over great and is also quieter
than the normal airring

to get the air to the easy i have connected one end of the horseshoe to 15 mm john guest pipe with a valve on and connected this to the original easy airpipe(using a piece of 15mm felxible pipe over the original pipe this fits into 15mm john guest fitting) - as soon as you open the valve airgoes to the nexus

hope this helps
Brians

[Casper Chapman]

But the standard Nexus with the correct air pump ciculates the correct amount of K1, why faff around modifying something that might have a problerm if not working correctly from manufacture?
Poorly circulating K1 can cause bacteria problems.....trust me i have been there.

[brians]

the airline in the bio system is probably the most altered part of the nexus either by drilling more holes, bigger holes or upgrading the line to 15mm pipe
i was using an airtech 60 which should be capable of turning over between 75 and 100 litres k1 and it was not happening
i was not getting good turnover of the k1 and as you rightly say poor turnover can lead to problems
by putting 6 airstones in the difference in turnover of k1 is massive and to my mind worth trying
( i have also seen a couple of dealers just hang 2 airdiffusers into nexus to get better turnover)


Brians

[Chagoiboy]

thanks. May have a mess around with some airstones. Are they now on the bottom and not 8" off the bottom like the air ring is?
My only alternative is to buy another airpump, a 120l i guess (or what ea now call the 150l) but my numbers didnt come-up this week.
How does everyones k1 behave after the air is turned off, does it ALL float? Some of mine floats but majority sinks..

[herbie]

When I turn off the air & pump all the K1 & K3 floats
in my Nexus 200

Best Regards

[dave13]

Hello Chagoiboy
Hard water ?
I had same problem last year 90 per cent on bottom. Spoke to evolution aqua and came to conclusion it was limescale. Told to put handful of k1 in glass of water and add descaler (kettles ) if k1 starts to float you know its limescale. Solution is to buy brick acid (5 litres £12) and add to k1 in nexus after draining out as much water as possible( down to air ring ). It will foam and look awful, and after 20-30 mins flush to waste repeating 7 or 8 times . K1 should circulate great afterwards.
Hope this helps.
Regards Dave.

[dave13]

Hi Chagoiboy
sorry forgot to say 10 litres brick acid worked best for my second 200 nexus/ 5 litres in first nexus left half k1 still on bottom.
I would guess 15 litres for 300 nexus. Fish were fine afterwards and so was nexus.( brick acid sold in plastic containers ).
Will not have this again, gone down R O route since.
Regards Dave.

[Chagoiboy]

yep hard water here, could be limescale i guess. Not keen on 100% killing my biomass though

[dave13]

Hi chagoiboy.
Put a weeks wages on its limescale, if your not heated you won't have alot of biomass and now is as good a time as any. Alternatively you could save floating k1 to other containers and just treat whats on the bottom. My k1 buoyancy was like new afterwards and it was quite apparent my nexuses had been underpreforming for sometime with no more build up at outlet. I think there are 100's of people out there with limescale affecting their k1 but don't realise it, thinking its a airpump/blocked airline issue and not knowing half of their k1 is sunk on bottom of nexus. Big problem is that my k1 was only 3 years old when treaded and would have to treat with brick acid every 24 months for optimum performance which is not ideal for biomass, glad have gone over to R O water.

Regards Dave.

[pkember]

Hi,

I had to do the 'brick acid' trick for the oldest of my Nexus 200 to clear the limescale build up as well. This was following advice from EA when I called them as I was suffering from the same prblems as you appear to be,


Paul

[Jonathan]

I had a similar problem which I solved by disconnecting the air supply and then putting a good blast of air, from a divers compressed air bottle, down the pipe. That obviously cleared all the crud from the holes and it now works as good as new.