What size was the heater ?
In theory a 2 kw Elecro heater should heat 2,000 gallons, but a 4kw would be better, the Elecro Titanium with digital thermostat in my opinion is the best of the electric heaters. NOT with time switch, just rely on the thermostat,
a time clock will create horendous problems with fluctuating temperature resulting in white spot etc.
As you already know ! you MUST have the correct wire and on/off switch box and trip switch on the Consumer Unit to cope with the load, or it will melt and could potentially combust !!!
To solve the immediate problem , STOP feeding,
KUSURI SUPER C or better still Envirex,
also Bactapur Sludgebusters,
you can't really overdose with these, so I would use a full dose am and another pm on the first day. ( Envirex is the best BUT £50 for a 2kg tub !!! Super C is almost as good and is £32 for 3 kg bag )
mix up as per instructions and put some in both Nexus and the rest in the pond. This will almost instantly neutralise decomposing sludge / solids / leaves etc. and any ammonia and nitrite,
continue water changes 10 % at a time.
Re-dose with kUSURI Super c or Envirex. the next day, then once per week.
They biologically clean filter media etc with natural enzymes, helping the good nitrifying and de-nitrifying bacteria to flourish and reproduce, but the cold will cause it to die back !!!
Keep Sludgebusters and any bacteria you buy in a warm place, and it will grow in the container. ( my pond is heated, but I still keep Sludgebusters next to the central heating boiler in winter ( keep safely away from kids !!! )
I'm suspecting no bottom drain (s) in the pond, am I right ?
as 1 Nexus can play with 2000 gallons, let alone 2 !!!
If NO bottom drains, you need a pond vacuum QUICK !!! to get the sludge out of the bottom of the pond. £99 for a decent one, £200 for a good one.
Any ice on the pond MUST NOT be broken by any hitting with anything, the shock wave can kill the Koi !!! Use a bucket of hot water ! This will allow the toxic gases to exit the pond water much more quickly.
If the top up water does not go through a proper in date filter, then de-chlorinator MUST be used or you will burn the gills with the chlorine in the tap water.
Don't worry about not feeding, you should NOT be feeding at all, if not heated
they can NOT digest any food at these low temperatures and as well as polluting the water, any food they do swallow will decompose inside a Koi's gut and cause bacterial problems inside the gut ! ( quite literally the food will rot inside the koi !!! ) their stomach is not a stomach at all, it's just a tube like our colon.
Don't give up on Koi, just get the fine tuning right !
You have 2 Nexus filters you say, which models ?
you have done the expensive bit and got the best filters in the world,
all you need to do is the little things now, and you'll be addicted to Koi !
There is something not right, either no bottom drain, or feeding in a cold pond, or the pump is not producing enough flow through the pair of Nexus,
you just need to diagnose the cause then problem fixed and enjoy your Koi.
A protein skimmer will remove the protein and the froth / brown water,
so will a bottle of anti-foam, BUT it is the CAUSE that needs fixing, THEN there will be no foam !
Peter.
