The Tropical Fruit Forum

There are also historic Citrus trees in Japan, dating back several hundred years.
In the USA there are several historic Citrus trees, such as the Parent Washington Navel, dating back to 1873, close enough to 150 years.
( You Do The Math, always wanted to say that ! )

If you take budwood from such an historic tree and graft onto rootstock, generally you will get a renewed and vigorous tree.
If you can select highly vigorous shoots from a flush or water shoots, you may even get a thorny juvenile type tree as a result.
Many of the popular varieties of Citrus are at least 50 years old, and regularly propagated by budding.
Overall there are few problems if any, with this process in producing healthy Citrus trees.
Where trees are maintained as budwood trees, regular pruning for budwood flush produces younger growth.
In many cases Citrus trees can be screened for Virus, and heat treated or shoot tip grafted to eliminate Viruses.
This will reinvigorate an old variety, and remove some of the decline factors.
Many Citrus varieties can also be renewed by growing Nucellar Clonal Seeds. These will be genetically identical to the parent, but fully juvenile.
These will essentially reset the clock back to zero for that Citrus variety.

Great question, I asked a similar one on this topic about Valentine.
https://tropicalfruitforum.com/index.php?topic=50675.0

Valentine is not available in Australia.
It sounds like a great type from the parental varieties, but seems to have mixed opinions on the fruit ?
Any comment on is it worth the effort to chase down ?

Any idea if the D. macrantha fruit came a tree in the Townsville area?

interesting you bring up Mendel, modern statistics shows he almost certainly fabricated his data to make dna appear more linear and less random! I think his heart was in the right place but still, bet he never expected that

Not sure he fabricated the data to get a fraudulent result, as has been the case with others.
Possibly he included results that fit best, and ignored results that didn't fit well ?
Ultimately he was correct in what he saw, and made a great leap into later understanding.

With composting you are feeding microbes to break down organic matter.
I'm sure the fish tank change water would be of benefit to the compost microbes, but maybe more beneficial direct to plants.

Seaweed has been used as a fertiliser in many regions where it is easily available.
On some of the British Channel Islands it was a big part of the fertiliser use, possibly with sheep manure. Not sure they had much else on those remote islands.
As you are probably diluting your seaweed harvest for spraying or applying small amounts of powder to soil or pots,
the amount of extra Sodium you actually apply is probably quite low.
You may want to watch out for doubling up the Sodium from other sources, ie your water supply, recycled grey water containing some detergents/soaps, water conditioners.
Otherwise unless you are going crazy, it should be ok.
Any thoughts on the actual Aquarium water, it contains fish wastes.
If you dilute it with fresh, the salt will drop.
I use our freshwater Aquarium water on pot plants when the water is changed.

The seasalt minerals in the algae are beneficial. The excess seasalt on the outside of the plant is possibly a problem. I believe it is washed off kelp before it is processed into plant fertiliser.

Is it okay to use river sand that contains bits of seashells? Or can this be too much calcium?

The rate of adding super fine Ag Lime and Dolomite Lime to Peat based and Coir based pot mix is 1kg to 2 kg of each per cubic metre, when mixing the pot mix.
This is to adjust the pH and supply Ca and Mg for a long period.
This is very fine ground powder, with a fast release rate for Calciim and Magnesium.
Intact shell and large pieces are going to be much slower acting.
Really it depends on the % of shell in the sand, the pH of the pot mix, and any other Calcium fertilisers, and the Calcium in your water supply all adding up to total Calcium.
You could probably sieve a sample of the sand and work out the % of shells.
Unless the % shells is high, it probably won't make much difference.
Do you have water snails etc in your Rivers ?
We get a few shells in our riversand, snail and mussel, but never that much.

Edit. possibly the most important factor is the % of sand you are using in the pot mix.
If you are using a large % of sand, the shells will factor more.
If you are using low % sand, ( say 2 to 5 % ),  the shells will be less in the total pot mix, and will have less effect.

Bull Kelp is a deep water cold species that contains high levels of plant growth stimulants. The live plants grow tall quickly to reach the light.
Apart from the other minerals it contains, the plant growth stimulants make it an useful "fertiliser".

There seems to be a few " Red Limes". 
Some of the Rangpur types are called Red Limes, but they seem to be pretty much Rangpur with orange or darker orange skin.
https://citrusvariety.ucr.edu/citrus-varieties/category-or-type/rangpur-limes
None of there are particularly red.
A lot of these are very similar, possibly some have been lost and mixed up over the years ?
Excalibur Red Lime is on this list, not strictly a Rangpur, but not red pulped either.

There are also Red Limes that have red skin and red pulp, a little more mandarin like with sour juice.
Anybody growing any of these ?
Some on the Citrusgrowersforum posted pics years ago.

Horticultural wetting agents when applied at correct rates should wet up pot mix, and as a surfactant, increase drainage
Something similar to a clean windscreen or kitchen sink. The water flows away after soap is applied.
Too much wetting agent can cause big problems with excess water holding.

Copper sulfate is used as an algicide and root killer. When using it as a fungicide, it is important to neutralize its acidity (3 to 4) with lime or other plant friendly pH raising agent to a pH of 7. Low pH increases absorption by plants to possibly toxic levels. I believe copper sulfate has been replaced with other copper molecules because it is inefficient and leads to excessive copper accumulation in soil, which at high toxic levels is harmful to roots, blocks iron absorption and disrupts photosynthesis. Copper soaps (Cueva) and copper oxide (Nordox) work similarly as a fungicide with less copper and less worries about pH and toxicity.

Thanks, you raise important points.
Copper Oxychloride is used heavily on grapevines around here, the Cu issues are a concern after decades of use.
As Copper Oxychloride washes off with rain, several sprays are required per season. Overhead irrigation will be the same.
If Bordeaux spray persists better, less sprays may be required per season.
That may or may not be less actual Cu Copper applied over time, depending on the chemical formulation and spray formulation.
The same for the other copper products.
I have used Copper Oxide, seemed similar holding to Oxychloride, but that is just a just an observation.
The Bourdeaux mix proportions of Copper and Lime will affect activity of the Copper, probably the persistence on the leaves and ease of spraying through nozzles.
Highly efficient low volume spray nozzles will allow good leaf coverage without using too much spray mix. ( for all  Copper sprays ).
To dilute the amount of Copper applied and increase the stick, I used Copper Oxychloride and powdered milk as a painted paste on trunks and wounds.
Somewhere between 30% Copper & 70% milk powder to 50/50 each.
As for Copper toxicity issues, those with a few trees sprayed can collect the fallen leaves and dispose or burn/ compost and spread more widely around than just under the same tree.